Issue Error Drupal <=> Plesk <=> MySQL-DB

[Kulturmensch]

Server operating system version

Ubuntu 20.04.5 LTS

Plesk version and microupdate number

Plesk Obsidian v18.0.46

Config: Ubuntu 20.04.5 LTS, MariaDB 10.6.9, PHP 8.1, Drupal 9.45, nginx/1.20.2

I receive these nginx-errors once I try to add new values to the Drupal-module "Metatag". Can anybody explain me what these errors mean and how to fix it?

/var/www/vhosts/.../httpdocs/web/core/lib/Drupal/Core/EventSubscriber/ExceptionLoggingSubs...PHP message: PDOException: SQLSTATE[HY000] No such file or directory in /var/www/vhosts/.../httpdocs/web/core/modules/dblog/src/Logger/DbLog.php on line 101 #0 /var/www/vhosts/.../httpdocs/web/core/modules/mysql/src/Driver/Database/mysql/Connection.php(189): PDO->__construct()
#1 /var/www/vhosts/.../httpdocs/web/core/lib/Drupal/Core/Database/Database.php(411): Drupal\mysql\Driver\Database\mysql\Connection:pen()
#2 /var/www/vhosts/.../httpdocs/web/core/lib/Drupal/Core/Database/Database.php(189): Drupal\Core\Database\Database:penConnection()
#3 /var/www/vhosts/.../httpdocs/web/core/modules/dblog/src/Logger/DbLog.php(101): Drupal\Core\Database\Database::getConnection()
#4 /var/www/vhosts/.../httpdocs/web/core/lib/Drupal/Core/Logger/LoggerChannel.php(127): Drupal\dblog\Logger\DbLog->log()
#5 /var/www/vhosts/.../httpdocs/web/core/lib/Drupal/Core/EventSubscriber/ExceptionL