Collabora problems - related to conversion of png file?

I have collabora and OnlyOffice in two Docker-containers on Ubuntu 18.04 and Nginx.
It has worked without problems. But one week ago I got an error which has caused som trouble. The service still works but it may be one reason for the slowdown.
I do not know but to me it seems this is related to collabora as collabora is listening on post 9980. I find POST /lool/convert-to/png in the log and it may have been that I tried to include a picture from my camera to a document (just an hypothesis).
I have stopped the collabora docker which solves the problem for now, but would like to have a definite solution.

Below the error code
2019/09/11 12:38:56 [error] 660#660: *3 FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught Doctrine\DBAL\DBALException: Failed to connect to the database: An exception occurred in driver: SQLSTATE[HY000] [2002] No such file or directory in /var/www/nextcloud/lib/private/DB/Connection.php:64
Stack trace:
#0 /var/www/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(448): OC\DB\Connection->connect()
#1 /var/www/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(410): Doctrine\DBAL\Connection->getDatabasePlatformVersion()
#2 /var/www/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(354): Doctrine\DBAL\Connection->detectDatabasePlatform()
#3 /var/www/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(710): Doctrine\DBAL\Connection->getDatabasePlatform()
#4 /var/www/nextcloud/lib/private/DB/Connection.php(151): Doctrine\DBAL\Connection->setTransactionIsolation(2)
#5 /var/www/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/DriverManager.php(181): OC\DB\Connection->__construct(Array, Objec…PHP message: PHP Fatal error: Uncaught Doctrine\DBAL\DBALException: Failed to connect to the database: An exception occurred in driver: SQLSTATE[HY000] [2002] No such file or directory in /var/www/nextcloud/lib/private/DB/Connection.php:64
Stack trace:
#0 /var/www/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(448): OC\DB\Connection->connect()
#1 /var/www/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(410): Doctrine\DBAL\Connection->getDatabasePlatformVersion()
#2 /var/www/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(354): Doctrine\DBAL\Connection->detectDatabasePlatform()
#3 /var/www/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(710): Doctrine\DBAL\Connection->getDatabasePlatform()
#4 /var/www/nextcloud/lib/private/DB/Connection.php(151): Doctrine\DBAL\Connection->setTransactionIsolation(2)
#5 /var/www/nextcloud/3rdparty/doctrine/dbal/lib/Doctrine/DBAL/DriverManager.php(181
2019/09/11 12:40:15 [error] 659#659: *42 connect() failed (111: Connection refused) while connecting to upstream, client: xxx.xxx.xx.xxx, server:mydomain.com, request: “GET /hosting/capabilities HTTP/1.1”, upstream: “https://127.0.0.1:9980/hosting/capabilities”, host: “mydomain.com
2019/09/11 12:40:15 [warn] 659#659: *42 upstream server temporarily disabled while connecting to upstream, client: xxx.xxx.xx.xxx, server:mydomain.com, request: “GET /hosting/capabilities HTTP/1.1”, upstream: “https://127.0.0.1:9980/hosting/capabilities”, host: “mydomain.com
2019/09/11 12:40:15 [error] 659#659: *42 connect() failed (111: Connection refused) while connecting to upstream, client: xxx.xxx.xx.xxx, server:mydomain.com, request: “GET /hosting/capabilities HTTP/1.1”, upstream: “https://127.0.0.1:9980/hosting/capabilities”, host: “mydomain.com
2019/09/11 12:40:15 [warn] 659#659: *42 upstream server temporarily disabled while connecting to upstream, client: xxx.xxx.xx.xxx, server:mydomain.com, request: “GET /hosting/capabilities HTTP/1.1”, upstream: “https://127.0.0.1:9980/hosting/capabilities”, host: “mydomain.com
2019/09/11 14:30:56 [warn] 659#659: *1236 a client request body is buffered to a temporary file /var/lib/nginx/body/0000000001, client: xxx.xxx.xx.xxx, server:mydomain.com, request: “POST /lool/convert-to/png HTTP/1.1”, host: “mydomain.com
2019/09/11 14:30:56 [error] 659#659: *1236 connect() failed (111: Connection refused) while connecting to upstream, client: xxx.xxx.xx.xxx, server:mydomain.com, request: “POST /lool/convert-to/png HTTP/1.1”, upstream: “https://127.0.0.1:9980/lool/convert-to/png”, host: “mydomain.com
2019/09/11 14:30:56 [warn] 659#659: *1236 upstream server temporarily disabled while connecting to upstream, client: xxx.xxx.xx.xxx, server:mydomain.com, request: “POST /lool/convert-to/png HTTP/1.1”, upstream: “https://127.0.0.1:9980/lool/convert-to/png”, host: “mydomain.com
2019/09/11 14:30:56 [error] 659#659: *1236 connect() failed (111: Connection refused) while connecting to upstream, client: xxx.xxx.xx.xxx, server:mydomain.com, request: “POST /lool/convert-to/png HTTP/1.1”, upstream: “https://127.0.0.1:9980/lool/convert-to/png”, host: “mydomain.com
2019/09/11 14:30:56 [warn] 659#659: *1236 upstream server temporarily disabled while connecting to upstream, client: xxx.xxx.xx.xxx, server:mydomain.com, request: “POST /lool/convert-to/png HTTP/1.1”, upstream: “https://127.0.0.1:9980/lool/convert-to/png”, host: “mydomain.com
2019/09/11 14:35:54 [warn] 659#659: *1333 a client request body is buffered to a temporary file /var/lib/nginx/body/0000000002, client: xxx.xxx.xx.xxx, server:mydomain.com, request: “POST /lool/convert-to/png HTTP/1.1”, host: “mydomain.com
2019/09/11 14:35:54 [error] 659#659: *1333 connect() failed (111: Connection refused) while connecting to upstream, client: xxx.xxx.xx.xxx, server:mydomain.com, request: “POST /lool/convert-to/png HTTP/1.1”, upstream: “https://127.0.0.1:9980/lool/convert-to/png”, host: “mydomain.com
2019/09/11 14:35:54 [warn] 659#659: *1333 upstream server temporarily disabled while connecting to upstream, client: xxx.xxx.xx.xxx, server:mydomain.com, request: “POST /lool/convert-to/png HTTP/1.1”, upstream: “https://127.0.0.1:9980/lool/convert-to/png”, host: “mydomain.com
2019/09/11 14:35:54 [error] 659#659: *1333 connect() failed (111: Connection refused) while connecting to upstream, client: xxx.xxx.xx.xxx, server:mydomain.com, request: “POST /lool/convert-to/png HTTP/1.1”, upstream: “https://127.0.0.1:9980/lool/convert-to/png”, host: “mydomain.com
2019/09/11 14:35:54 [warn] 659#659: *1333 upstream server temporarily disabled while connecting to upstream, client: xxx.xxx.xx.xxx, server:mydomain.com, request: “POST /lool/convert-to/png HTTP/1.1”, upstream: “https://127.0.0.1:9980/lool/convert-to/png”, host: “mydomain.com
2019/09/11 14:35:56 [error] 659#659: *1337 no live upstreams while connecting to upstream, client: xxx.xxx.xx.xxx, server:mydomain.com, request: “GET /hosting/discovery HTTP/1.1”, upstream: “https://localhost/hosting/discovery”, host: “mydomain.com