DB exception: Access denied for user

I have a NextCloudPi server running in docker for quite some while. Today it suddenly stopped syncing.

The admin UI shows that all services are up, however the Nextcloud check shows error . All auto-updates are enabled.

The diagnostics show that access is denied to the DB. This is strange, as I didn’t change anything on the server recently.

Here’s my nextCloud report.

NextCloudPi diagnostics

NextCloudPi version  v1.25.0
NextCloudPi image    NextCloudPi_docker_03-20-20
distribution         Debian GNU/Linux 10 \n \l
automount            no
USB devices          sda
datadir              /data/nextcloud/data
data in SD           no
data filesystem      ext2/ext3
data disk usage      780G/916G
rootfs usage         9.9G/12G
swapfile             /var/swap
dbdir                /data/database
Nextcloud check      error
HTTPD service        up
PHP service          up
MariaDB service      up
Redis service        up
Postfix service      up
internet check       ok
port check 80        open
port check 443       open
IP                   ***REMOVED SENSITIVE VALUE***
gateway              ***REMOVED SENSITIVE VALUE***
interface            eth0
certificates         ***REMOVED SENSITIVE VALUE***
NAT loopback         no
uptime               11:58

Nextcloud configuration

An unhandled exception has been thrown:
Doctrine\DBAL\DBALException: Failed to connect to the database: An exception occurred in driver: SQLSTATE[HY000] [1045] Access denied for user 'ncadmin'@'localhost' (using password: YES) in /data/nextcloud/lib/private/DB/Connection.php:68
Stack trace:
#0 /data/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(420): OC\DB\Connection->connect()
#1 /data/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(380): Doctrine\DBAL\Connection->getDatabasePlatformVersion()
#2 /data/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(324): Doctrine\DBAL\Connection->detectDatabasePlatform()
#3 /data/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(683): Doctrine\DBAL\Connection->getDatabasePlatform()
#4 /data/nextcloud/lib/private/DB/Connection.php(155): Doctrine\DBAL\Connection->setTransactionIsolation(2)
#5 /data/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/DriverManager.php(195): OC\DB\Connection->__construct(Array, Object(Doctrine\DBAL\Driver\PDOMySql\Driver), Object(Doctrine\DBAL\Configuration), Object(Doctrine\Common\EventManager))
#6 /data/nextcloud/lib/private/DB/ConnectionFactory.php(157): Doctrine\DBAL\DriverManager::getConnection(Array, Object(Doctrine\DBAL\Configuration), Object(Doctrine\Common\EventManager))
#7 /data/nextcloud/lib/private/Server.php(749): OC\DB\ConnectionFactory->getConnection('mysql', Array)
#8 /data/nextcloud/3rdparty/pimple/pimple/src/Pimple/Container.php(118): OC\Server->OC\{closure}(Object(OC\Server))
#9 /data/nextcloud/lib/private/ServerContainer.php(125): Pimple\Container->offsetGet('OCP\\IDBConnecti...')
#10 /data/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(162): OC\ServerContainer->query('OCP\\IDBConnecti...')
#11 /data/nextcloud/3rdparty/pimple/pimple/src/Pimple/Container.php(114): OC\AppFramework\Utility\SimpleContainer->OC\AppFramework\Utility\{closure}(Object(OC\Server))
#12 /data/nextcloud/lib/private/ServerContainer.php(125): Pimple\Container->offsetGet('DatabaseConnect...')
#13 /data/nextcloud/lib/private/Server.php(1666): OC\ServerContainer->query('DatabaseConnect...')
#14 /data/nextcloud/lib/private/Server.php(422): OC\Server->getDatabaseConnection()
#15 /data/nextcloud/3rdparty/pimple/pimple/src/Pimple/Container.php(118): OC\Server->OC\{closure}(Object(OC\Server))
#16 /data/nextcloud/lib/private/ServerContainer.php(125): Pimple\Container->offsetGet('OC\\Authenticati...')
#17 /data/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(70): OC\ServerContainer->query('OC\\Authenticati...', true)
#18 /data/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(100): OC\AppFramework\Utility\SimpleContainer->buildClass(Object(ReflectionClass))
#19 /data/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(115): OC\AppFramework\Utility\SimpleContainer->resolve('OC\\Authenticati...')
#20 /data/nextcloud/lib/private/ServerContainer.php(150): OC\AppFramework\Utility\SimpleContainer->query('OC\\Authenticati...', true)
#21 /data/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(70): OC\ServerContainer->query('OC\\Authenticati...', true)
#22 /data/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(100): OC\AppFramework\Utility\SimpleContainer->buildClass(Object(ReflectionClass))
#23 /data/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(115): OC\AppFramework\Utility\SimpleContainer->resolve('OC\\Authenticati...')
#24 /data/nextcloud/lib/private/ServerContainer.php(150): OC\AppFramework\Utility\SimpleContainer->query('OC\\Authenticati...', true)
#25 /data/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(162): OC\ServerContainer->query('OC\\Authenticati...')
#26 /data/nextcloud/3rdparty/pimple/pimple/src/Pimple/Container.php(114): OC\AppFramework\Utility\SimpleContainer->OC\AppFramework\Utility\{closure}(Object(OC\Server))
#27 /data/nextcloud/lib/private/ServerContainer.php(125): Pimple\Container->offsetGet('OC\\Authenticati...')
#28 /data/nextcloud/lib/private/Server.php(434): OC\ServerContainer->query('OC\\Authenticati...')
#29 /data/nextcloud/3rdparty/pimple/pimple/src/Pimple/Container.php(118): OC\Server->OC\{closure}(Object(OC\Server))
#30 /data/nextcloud/lib/private/ServerContainer.php(125): Pimple\Container->offsetGet('OC\\User\\Session')
#31 /data/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(162): OC\ServerContainer->query('OC\\User\\Session')
#32 /data/nextcloud/3rdparty/pimple/pimple/src/Pimple/Container.php(114): OC\AppFramework\Utility\SimpleContainer->OC\AppFramework\Utility\{closure}(Object(OC\Server))
#33 /data/nextcloud/lib/private/ServerContainer.php(125): Pimple\Container->offsetGet('UserSession')
#34 /data/nextcloud/lib/private/Server.php(1542): OC\ServerContainer->query('UserSession')
#35 /data/nextcloud/lib/private/Server.php(802): OC\Server->getUserSession()
#36 /data/nextcloud/3rdparty/pimple/pimple/src/Pimple/Container.php(118): OC\Server->OC\{closure}(Object(OC\Server))
#37 /data/nextcloud/lib/private/ServerContainer.php(125): Pimple\Container->offsetGet('OC\\App\\AppManag...')
#38 /data/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(162): OC\ServerContainer->query('OC\\App\\AppManag...')
#39 /data/nextcloud/3rdparty/pimple/pimple/src/Pimple/Container.php(114): OC\AppFramework\Utility\SimpleContainer->OC\AppFramework\Utility\{closure}(Object(OC\Server))
#40 /data/nextcloud/lib/private/ServerContainer.php(125): Pimple\Container->offsetGet('AppManager')
#41 /data/nextcloud/lib/private/Server.php(1837): OC\ServerContainer->query('AppManager')
#42 /data/nextcloud/lib/private/legacy/app.php(347): OC\Server->getAppManager()
#43 /data/nextcloud/lib/private/legacy/app.php(114): OC_App::getEnabledApps()
#44 /data/nextcloud/lib/base.php(645): OC_App::loadApps(Array)
#45 /data/nextcloud/lib/base.php(1089): OC::init()
#46 /data/nextcloud/console.php(48): require_once('/data/nextcloud...')
#47 /data/nextcloud/occ(11): require_once('/data/nextcloud...')
#48 {main}
HTTPd logs

[Wed May 06 20:56:48.984817 2020] [authz_host:error] [pid 94:tid 2765394976] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /img/toggle.svg failed, reason: unable to get the remote host name
[Wed May 06 20:56:48.993684 2020] [authz_host:error] [pid 94:tid 2765394976] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /img/reboot.svg failed, reason: unable to get the remote host name
[Wed May 06 20:56:48.999645 2020] [authz_host:error] [pid 94:tid 2765394976] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /img/ncp-logo.svg failed, reason: unable to get the remote host name, referer: https://192.168.1.19:4443/css/ncp.css
[Wed May 06 20:56:49.009537 2020] [authz_host:error] [pid 94:tid 2765394976] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /img/search.svg failed, reason: unable to get the remote host name, referer: https://192.168.1.19:4443/css/ncp.css
[Wed May 06 20:56:49.011868 2020] [authz_host:error] [pid 94:tid 2765394976] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /img/nc-button.svg failed, reason: unable to get the remote host name, referer: https://192.168.1.19:4443/css/ncp.css
[Wed May 06 20:56:49.012739 2020] [authz_host:error] [pid 94:tid 2790573088] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /img/dashboard.svg failed, reason: unable to get the remote host name, referer: https://192.168.1.19:4443/css/ncp.css
[Wed May 06 20:56:49.014047 2020] [authz_host:error] [pid 94:tid 2790573088] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /img/defaults-white.svg failed, reason: unable to get the remote host name, referer: https://192.168.1.19:4443/css/ncp.css
[Wed May 06 20:56:49.015729 2020] [authz_host:error] [pid 94:tid 2790573088] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /img/settings-white.svg failed, reason: unable to get the remote host name, referer: https://192.168.1.19:4443/css/ncp.css
[Wed May 06 20:56:49.030160 2020] [authz_host:error] [pid 94:tid 2765394976] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /img/info-white.svg failed, reason: unable to get the remote host name, referer: https://192.168.1.19:4443/css/ncp.css
[Wed May 06 20:56:49.030252 2020] [authz_host:error] [pid 94:tid 2757002272] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /img/info.svg failed, reason: unable to get the remote host name, referer: https://192.168.1.19:4443/css/ncp.css
[Wed May 06 20:56:49.030359 2020] [authz_host:error] [pid 94:tid 2790573088] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /img/wizard.svg failed, reason: unable to get the remote host name, referer: https://192.168.1.19:4443/css/ncp.css
[Wed May 06 20:56:49.030287 2020] [authz_host:error] [pid 94:tid 2798965792] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /img/files.svg failed, reason: unable to get the remote host name, referer: https://192.168.1.19:4443/css/ncp.css
[Wed May 06 20:56:49.032259 2020] [authz_host:error] [pid 94:tid 2773787680] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /img/poweroff.svg failed, reason: unable to get the remote host name, referer: https://192.168.1.19:4443/css/ncp.css
[Wed May 06 20:56:49.046750 2020] [authz_host:error] [pid 94:tid 2773787680] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /ncp-output.php failed, reason: unable to get the remote host name
[Wed May 06 20:56:49.052548 2020] [authz_host:error] [pid 94:tid 2798965792] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /ncp-launcher.php failed, reason: unable to get the remote host name
[Wed May 06 20:56:49.307499 2020] [authz_host:error] [pid 94:tid 2790573088] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /img/favicon.png failed, reason: unable to get the remote host name
[Wed May 06 20:56:54.657806 2020] [authz_host:error] [pid 94:tid 2798965792] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /ncp-launcher.php failed, reason: unable to get the remote host name
[Wed May 06 20:56:54.684409 2020] [authz_host:error] [pid 94:tid 2790573088] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /img/download.svg failed, reason: unable to get the remote host name
[Wed May 06 20:56:54.684408 2020] [authz_host:error] [pid 94:tid 2798965792] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /ncp-launcher.php failed, reason: unable to get the remote host name
[Wed May 06 20:56:54.684668 2020] [authz_host:error] [pid 94:tid 2790573088] [client 192.168.1.106:64373] AH01753: access check of 'localhost' to /img/delete.svg failed, reason: unable to get the remote host name

Database logs

2020-05-07  8:12:10 4421 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:10 4422 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:10 4423 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:10 4424 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:17 4425 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:17 4426 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:17 4427 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:17 4428 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:17 4429 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:17 4430 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:17 4431 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:17 4432 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:19 4433 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:19 4434 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:19 4435 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:19 4436 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:24 4437 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:24 4438 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:24 4439 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)
2020-05-07  8:12:24 4440 [Warning] Access denied for user 'ncadmin'@'localhost' (using password: YES)

Nextcloud logs

{"reqId":"XrBNkU7-HlwnOq@F0peORgAAAJU","level":3,"time":"2020-05-04T19:14:57+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"file_get_contents(/data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg): failed to open stream: No such file or directory at /data/nextcloud/lib/private/Files/Storage/Local.php#218","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBNkU7-HlwnOq@F0peORgAAAJU","level":3,"time":"2020-05-04T19:14:57+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"stat(): stat failed for /data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg at /data/nextcloud/lib/private/Files/Storage/Local.php#144","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBNkU7-HlwnOq@F0peORgAAAJU","level":3,"time":"2020-05-04T19:14:57+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"filesize(): stat failed for /data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg at /data/nextcloud/lib/private/LargeFileHelper.php#172","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBRyE7-HlwnOq@F0peOnQAAAIs","level":3,"time":"2020-05-04T19:32:56+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"file_get_contents(/data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg): failed to open stream: No such file or directory at /data/nextcloud/lib/private/Files/Storage/Local.php#218","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBRyE7-HlwnOq@F0peOnQAAAIs","level":3,"time":"2020-05-04T19:32:56+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"stat(): stat failed for /data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg at /data/nextcloud/lib/private/Files/Storage/Local.php#144","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBRyE7-HlwnOq@F0peOnQAAAIs","level":3,"time":"2020-05-04T19:32:56+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"filesize(): stat failed for /data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg at /data/nextcloud/lib/private/LargeFileHelper.php#172","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBSkj43KikGCfI@J-v7ugAAAFQ","level":3,"time":"2020-05-04T19:36:18+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"file_get_contents(/data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg): failed to open stream: No such file or directory at /data/nextcloud/lib/private/Files/Storage/Local.php#218","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBSkj43KikGCfI@J-v7ugAAAFQ","level":3,"time":"2020-05-04T19:36:18+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"stat(): stat failed for /data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg at /data/nextcloud/lib/private/Files/Storage/Local.php#144","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBSkj43KikGCfI@J-v7ugAAAFQ","level":3,"time":"2020-05-04T19:36:18+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"filesize(): stat failed for /data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg at /data/nextcloud/lib/private/LargeFileHelper.php#172","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBSkz43KikGCfI@J-v7vQAAAFU","level":3,"time":"2020-05-04T19:36:19+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"file_get_contents(/data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg): failed to open stream: No such file or directory at /data/nextcloud/lib/private/Files/Storage/Local.php#218","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBSkz43KikGCfI@J-v7vQAAAFU","level":3,"time":"2020-05-04T19:36:19+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"stat(): stat failed for /data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg at /data/nextcloud/lib/private/Files/Storage/Local.php#144","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBSkz43KikGCfI@J-v7vQAAAFU","level":3,"time":"2020-05-04T19:36:19+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"filesize(): stat failed for /data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg at /data/nextcloud/lib/private/LargeFileHelper.php#172","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBSkz43KikGCfI@J-v7vgAAAFA","level":3,"time":"2020-05-04T19:36:19+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"file_get_contents(/data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg): failed to open stream: No such file or directory at /data/nextcloud/lib/private/Files/Storage/Local.php#218","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBSkz43KikGCfI@J-v7vgAAAFA","level":3,"time":"2020-05-04T19:36:19+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"stat(): stat failed for /data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg at /data/nextcloud/lib/private/Files/Storage/Local.php#144","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBSkz43KikGCfI@J-v7vgAAAFA","level":3,"time":"2020-05-04T19:36:19+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"filesize(): stat failed for /data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg at /data/nextcloud/lib/private/LargeFileHelper.php#172","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBSkz43KikGCfI@J-v7vwAAAFM","level":3,"time":"2020-05-04T19:36:20+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"file_get_contents(/data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg): failed to open stream: No such file or directory at /data/nextcloud/lib/private/Files/Storage/Local.php#218","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBSkz43KikGCfI@J-v7vwAAAFM","level":3,"time":"2020-05-04T19:36:20+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"stat(): stat failed for /data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg at /data/nextcloud/lib/private/Files/Storage/Local.php#144","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"XrBSkz43KikGCfI@J-v7vwAAAFM","level":3,"time":"2020-05-04T19:36:20+02:00","remoteAddr":"172.25.0.5","user":"teamhejj","app":"PHP","method":"GET","url":"/index.php/core/preview.png?file=K%c3%a9pek/2020/02%20-%20Operab%c3%a1l%201.JPG&x=281&y=500&a=1&mode=cover","message":"filesize(): stat failed for /data/nextcloud/data/appdata_ocftle7uchwj/preview/359215/768-1024.jpg at /data/nextcloud/lib/private/LargeFileHelper.php#172","userAgent":"Mozilla/5.0 (iOS) Nextcloud-iOS/2.25.9","version":"18.0.4.2"}
{"reqId":"TXwV4zyUNMSg2uvyYcVC","level":2,"time":"2020-05-05T14:00:22+02:00","remoteAddr":"","user":"--","app":"appstoreFetcher","method":"","url":"--","message":"Could not connect to appstore: cURL error 28: Operation timed out after 10000 milliseconds with 4695435 out of 4808238 bytes received (see http://curl.haxx.se/libcurl/c/libcurl-errors.html)","userAgent":"--","version":"18.0.4.2"}
{"reqId":"XrK1xyX5YzAbm8eAvMoYvwAAAEU","level":3,"time":"2020-05-06T15:04:07+02:00","remoteAddr":"172.25.0.4","user":"--","app":"PHP","method":"GET","url":"/ocs/v2.php/apps/notifications/api/v2/notifications?format=json","message":"RedisException: NOAUTH Authentication required. at /data/nextcloud/lib/private/Memcache/Redis.php#54","userAgent":"Mozilla/5.0 (Windows) mirall/2.6.4stable-Win64 (build 20200303) (Nextcloud)","version":"18.0.4.2"}

I had the exact same issue, followed [SOLVED] Ncadmin database password and ncp update issues, restarted the docker container and it’s fixed. Unlike @acesabe I wasn’t messing with DB. NC just broke in a middle of a file upload.

Unfortunately that did not help. I ended up with recreating my nextcloud instance from scratch.