4.2 crashing on delete email - Doctrine issue

Your software
My Mautic version is: 4.2.0
My PHP version is: 7.4
My Database type and version is: mysqli 10.2.33-MariaDB-log (Doctrine\DBAL\Platforms\MariaDb1027Platform)

Your problem
My problem is: I’m trying to delete a test email that was used on a test campaign (cleaning up), connected to test contacts. When I do, the progress bar animates, then stops and the screen does not refresh. Clicking anything on Mautic does nothing, reloading that url does nothing. Loading any other mautic url says the system is offline (contact Admin). If I then wait around 30 seconds or so, Mautic reloads (without login) just fine.

These errors are showing in the Mautic log:
[2022-03-22 13:43:21] mautic.CRITICAL: Uncaught PHP Exception Doctrine\DBAL\Exception\ConnectionException: “An exception occurred in driver: Connection refused” at /home/path/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php line 112 {“exception”:"[object] (Doctrine\DBAL\Exception\ConnectionException(code: 0): An exception occurred in driver: Connection refused at /home/path/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php:112, Doctrine\DBAL\Driver\Mysqli\Exception\ConnectionFailed(code: 0): Connection refused at /home/path/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/Mysqli/Exception/ConnectionFailed.php:19)"}

These errors show on my server log:
[Tue Mar 22 17:43:27 2022] [error] [client] AH01071: Got error ‘PHP message: Doctrine\DBAL\DBALException: An exception occurred while establishing a connection to figure out your platform version.\nYou can circumvent this by setting a ‘server_version’ configuration value\n\nFor further information have a look at:\nhttps://github.com/doctrine/DoctrineBundle/issues/673 - in file /home/path/vendor/doctrine/doctrine-bundle/ConnectionFactory.php - at line 134’

Steps I have tried to fix the problem: logging out, clearing cache. Created new blank email (deleted fine). I browsed the Doctrine file mentioned in the server error, however can’t work out how to set a server_version as it guides.