Deployment hangs in initial db connection

I run V9.4.25 and deploy the same project, exactly the same database and the same deployment data
onto several linux servers of identical database engine (MariaDb) and same apache2 and php 7.2
of hostproviders in Switzerland.

The initial deployment asks for a deployment password and establishes the db connection. On one server it hangs after the production password is entered with a 504 server error, spcifically shows a timeout in
_lib/prod/lib/php/nm_ini_manager2.php (after some 60 sec). The effect can be reproduced.

Question : What in the configuration of that server is responsible for the hangup?