[pigeldi]

When I use "clean database" (is also executed automatically when updating the database), Ember suddenly hangs, meaning it never finishes the cleaning, no matter how long I wait. I can only kill it via the task manager. What could be the reason and how can I fix this? I currently cannot update the database anymore :-(

It needs very long time to do a deep clean. But you can disable "Clean Database after Update" in settings for movies and tv shows (Settings => Movies/TV Shows => Files and Sources).

That was not the issue, I did not have many movies. I found out what the problem was: After restarting the computer, it needed user/password to access one of the shares. However Ember did not tell me, it just waited forever, until I accessed the share in the explorer and typed in the credentials.
Would be helpful if Ember either terminates after some time with a message or could even ask for the credentials on its own.