Hey @Ralf_Karpa,
Thanks for giving that a try!
If Roon did not crash after testing on a fresh database, then the issue may potentially be linked to your database.
Had you done any metadata curation from a third-party software prior to importing it into Roon? Roon never modifies your track files, so many users make their edits prior to importing their library into Roon. Here are a few options to consider:
As a next step, do you have a backup that predates your issue? If yes, I would restore from that backup and test again. 