Nextcloud: Database connection refused

Hi all, is there an explanation why the NextCloud container (on unraid) keeps losing the MariaDB connection? I have now set up everything for the 2nd time and overnight the connection to DB is gone.

I fed adminer with the credentials from config.php and was able to log in to the DB. Therefore the credentials should be correct. Can it perhaps be due to the custom docker network? Here I have specified the internal IP and not the unraid server plus port.

Any suggestion to solve this?

Doctrine\DBAL\Exception: Failed to connect to the database: An exception occurred in the driver: SQLSTATE[HY000] [2002] Connection refused in /config/www/nextcloud/lib/private/DB/Connection.php:139
Stack trace:
#0 /config/www/nextcloud/3rdparty/doctrine/dbal/src/Connection.php(1519): OC\DB\Connection->connect()
#1 /config/www/nextcloud/3rdparty/doctrine/dbal/src/Connection.php(1041): Doctrine\DBAL\Connection->getWrappedConnection()
#2 /config/www/nextcloud/lib/private/DB/Connection.php(261): Doctrine\DBAL\Connection->executeQuery()
#3 /config/www/nextcloud/3rdparty/doctrine/dbal/src/Query/QueryBuilder.php(345): OC\DB\Connection->executeQuery()
#4 /config/www/nextcloud/lib/private/DB/QueryBuilder/QueryBuilder.php(281): Doctrine\DBAL\Query\QueryBuilder->execute()
#5 /config/www/nextcloud/lib/private/AppConfig.php(415): OC\DB\QueryBuilder\QueryBuilder->execute()
#6 /config/www/nextcloud/lib/private/AppConfig.php(180): OC\AppConfig->loadConfigValues()
#7 /config/www/nextcloud/lib/private/AppConfig.php(371): OC\AppConfig->getApps()
#8 /config/www/nextcloud/lib/private/legacy/OC_App.php(965): OC\AppConfig->getValues()
#9 /config/www/nextcloud/lib/private/Server.php(725): OC_App::getAppVersions()
#10 /config/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(162): OC\Server->OC{closure}()
#11 /config/www/nextcloud/3rdparty/pimple/pimple/src/Pimple/Container.php(122): OC\AppFramework\Utility\SimpleContainer->OC\AppFramework\Utility{closure}()
#12 /config/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(129): Pimple\Container->offsetGet()
#13 /config/www/nextcloud/lib/private/ServerContainer.php(136): OC\AppFramework\Utility\SimpleContainer->query()
#14 /config/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(57): OC\ServerContainer->query()
#15 /config/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(184): OC\AppFramework\Utility\SimpleContainer->get()
#16 /config/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(162): OC\AppFramework\Utility\SimpleContainer->OC\AppFramework\Utility{closure}()
#17 /config/www/nextcloud/3rdparty/pimple/pimple/src/Pimple/Container.php(118): OC\AppFramework\Utility\SimpleContainer->OC\AppFramework\Utility{closure}()
#18 /config/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(129): Pimple\Container->offsetGet()
#19 /config/www/nextcloud/lib/private/ServerContainer.php(136): OC\AppFramework\Utility\SimpleContainer->query()
#20 /config/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(57): OC\ServerContainer->query()
#21 /config/www/nextcloud/lib/private/Server.php(1119): OC\AppFramework\Utility\SimpleContainer->get()
#22 /config/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(162): OC\Server->OC{closure}()
#23 /config/www/nextcloud/3rdparty/pimple/pimple/src/Pimple/Container.php(122): OC\AppFramework\Utility\SimpleContainer->OC\AppFramework\Utility{closure}()
#24 /config/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(129): Pimple\Container->offsetGet()
#25 /config/www/nextcloud/lib/private/ServerContainer.php(136): OC\AppFramework\Utility\SimpleContainer->query()
#26 /config/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(57): OC\ServerContainer->query()
#27 /config/www/nextcloud/lib/private/Server.php(2070): OC\AppFramework\Utility\SimpleContainer->get()
#28 /config/www/nextcloud/lib/private/Files/View.php(117): OC\Server->getLockingProvider()
#29 /config/www/nextcloud/lib/private/Server.php(462): OC\Files\View->__construct()
#30 /config/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(162): OC\Server->OC{closure}()
#31 /config/www/nextcloud/3rdparty/pimple/pimple/src/Pimple/Container.php(122): OC\AppFramework\Utility\SimpleContainer->OC\AppFramework\Utility{closure}()
#32 /config/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(129): Pimple\Container->offsetGet()
#33 /config/www/nextcloud/lib/private/ServerContainer.php(136): OC\AppFramework\Utility\SimpleContainer->query()
#34 /config/www/nextcloud/lib/private/AppFramework/Utility/SimpleContainer.php(57): OC\ServerContainer->query()
#35 /config/www/nextcloud/lib/private/Server.php(1472): OC\AppFramework\Utility\SimpleContainer->get()
#36 /config/www/nextcloud/lib/base.php(617): OC\Server->boot()
#37 /config/www/nextcloud/lib/base.php(1144): OC::init()
#38 /config/www/nextcloud/cron.php(43): require_once(‘…’)
#39 {main}