Nextcloud stopped synching files with Desktop app and Android app

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Nextcloud version (eg, 20.0.5): 21.03
Operating system and version (eg, Ubuntu 20.04): Ubuntu 21.04 (GNU/Linux 5.11.0-25-generic x86_64)
Apache or nginx version (eg, Apache 2.4.25): Server version: Apache/2.4.46 (Ubuntu) Server built: 2021-06-17T17:09:41
PHP version (eg, 7.4): PHP 7.4.16 (cli) (built: Jul 5 2021 13:04:38) ( NTS )

The issue you are facing:
While the file sync worked fine all the time since installation of Nextcloud last year from all machines (Windows PC, Ubuntu Laptop, Android phone, Android tablet), a few days ago it all suddenly stopped working on all machines, without knowingly having changed anything. On the Windows and Ubuntu PC’s I run the latest version of the Desktop app (always updating as soon as a new release is announced by the Desktop app itself). On the Android hardware the apps also automatically update.
The Desktop apps for Linux and Windows show the same behaviour: in Settings they show an error with the text “Server replied with an error while reading directory ‘xxxxxx’ : Verbindung beendet” (Verbindung beendet = connection closed)
"[Path_and_Filename]: Server replied “500 Internal Server Error” to “PUT https://[Nextcloud_web_address]/remote.php/dav/files/[Username]/[Folder_and_Filename]”

The Android app throws an error in the notifications for each file it was unable to upload:
“Hochladen fehlgeschlagen Fehlerhaft Serverkonfiguration”, which translates to
“Upload failed Incorrect server configuration”
On Android, I can see that the files get uploaded (% is increasing from 0 to 100%), but obviously get dissaproved by the server.

At the same time, the syncing of calendar, tasks, and notes work without any issues.

Is this the first time you’ve seen this error? (Y/N):Yes, since a few days

Steps to replicate it:

  1. Force Sync on Desktop App or wait for next refresh on Android app

The output of your Nextcloud log in Admin > Logging:

The log is not showing anything

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

$CONFIG = array (
  'instanceid' => 'xxx',
  'passwordsalt' => 'xxx',
  'secret' => 'xxx',
  'trusted_domains' => 
  array (
    0 => 'xxx.local',
    1 => '',
  'datadirectory' => '/mnt/HD1/',
  'dbtype' => 'mysql',
  'version' => '',
  'overwrite.cli.url' => 'http://xxx.local',
  'dbname' => 'nextcloud',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => 'xxx',
  'dbpassword' => 'xxx',
  'installed' => true,
  'app_install_overwrite' => 
  array (
    0 => 'cookbook',
    1 => 'files_retention',
  'log_type' => 'file',
  'logtimezone' => 'Europe/Berlin',
  'logfile' => '/var/log/nextcloud.log',
  'loglevel' => 2,
  'syslog_tag' => 'Nextcloud',
  'maintenance' => false,
  'filesystem_check_changes' => 1,
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'overwriteprotocol' => 'https',
  'theme' => '',
  '' => 'stable',
  'mail_domain' => 'xxx',
  'mail_from_address' => 'xxx',
  'mail_smtpmode' => 'smtp',
  'mail_sendmailmode' => 'smtp',
  'mail_smtpauthtype' => 'LOGIN',
  'mail_smtpauth' => 1,
  'mail_smtphost' => 'xxx',
  'mail_smtpport' => '587',
  'mail_smtpsecure' => 'tls',
  'mail_smtpname' => 'xxx',
  'mail_smtppassword' => 'xxx',
  'default_phone_region' => 'xx',

The output of your Apache/nginx/system log in /var/log/apache2/access.log:
I do not know what to extract from that large file.


It seems this had to do with the reverse proxy server serving the nextcloud and other servers. The proxy server’s disk was full. After extending the disk space and thus supplying additional space, the Nextcloud started to fully function again. Not sure how this produced the behaviour described above. But this is resolved.