Today I upgraded again to 2.2.1 as suggested by piwik. Immediately after update, I have the same issue as in previous message(s), I solved in the same way, after this I checked and it is working but after some hours, when I want to check some visits, I was unable to login with (finally) this message:
Your Piwik configuration file appears to be misconfigured. You can either remove config/config.ini.php and resume installation, or correct the database connection settings.
SQLSTATE[HY000]  An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full.
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Somehow the installation started automatically.
I am totally lost. Any hints?