GitLab 10.3.3 500 after upgrade on multiple paths, mostly regarding projects

After an upgrade from 10.2-ee to 10.3.3-ee we cannot open /admin/application_settings anymore.

gitlab-rake db:migrate:status shows all up

gitlab-rake db:migrate does not do anything

gitlab-rake cache:clear and gitlab-ctl reconfigure have not helped

We get 2 warnings when running rake commands:

/opt/gitlab/embedded/service/gitlab-rails/lib/gitlab/git/repository.rb:24: warning: already initialized constant Gitlab::Git::Repository::GITALY_INTERNAL_URL
/opt/gitlab/embedded/service/gitlab-rails/lib/gitlab/git/repository.rb:21: warning: previous definition of GITALY_INTERNAL_URL was here

Traceback from Sentry: https://paste.ee/p/OtLOJ#0wTQAbUCbVsaLcrGzTogeMwF1raSe0oI