Unicorn keeps restarting

I’ve updated my GitLab instance to 11.8.1 and since my GitLab crash periodically (every day) and send 502 response. If I check the logs, I see these lines in /var/log/gitlab/unicorn/unicorn_stderr.log :

2019-03-27T13:08:44.726035627Z ArgumentError: Already running on PID:516 (or pid=/opt/gitlab/var/unicorn/unicorn.pid is stale)
2019-03-27T13:08:44.726045649Z /opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/unicorn-5.1.0/lib/unicorn/http_server.rb:195:in pid=' 2019-03-27T13:08:44.726055772Z /opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/unicorn-5.1.0/lib/unicorn/http_server.rb:127:in start’
2019-03-27T13:08:44.726065739Z /opt/gitlab/embedded/lib/ruby/gems/2.5.0/gems/unicorn-5.1.0/bin/unicorn:126:in <top (required)>' 2019-03-27T13:08:44.726075995Z /opt/gitlab/embedded/bin/unicorn:23:in load’
2019-03-27T13:08:44.726085507Z /opt/gitlab/embedded/bin/unicorn:23:in `<top (required)>’

So it seems that unicorn has crash and it tries to restart it but it can’t because the pid file is still here. But I can’t find in the logs the root cause of the first crash.
I’ve installed Gitlab with Docker.

If anyone has an idea on how I could find the reason of the crash it would be great !

Thanks in advance

Do you have any syslog logs? It might be that the process is killed due to an Out of Memory situation. The syslog logs should contain a line about this, if that happened