Hello @Ulf_Silbersky,
Thank you for the update.
We鈥檝e recently released an Early Access build that addresses most of the known issues related to macOS Tahoe:
Early Access: RoonServer 2.56 (Build 1566) and ARC 1.70 (Build 371)
Would you kindly follow the instructions in the article below to join the Early Access program and check if the issue persists on that version?
Roon Early Access Program