Update on my issue:
The problem was gone the next day after i did the update to 5.1. Not sure why, i didn’t change anything. So for now everything works fine again for me.
→ Update: Sorry, i mentioned the wrong version number. I am using 5.0.1 and this is the version i got the initial problems with. I cannot find any 5.1 at the moment so maybe articles writing about a 5.1 are not using the correct version number.