Airplay no longer working on M10v2 with BluOS 4.6.3

Hi,
my M10v2 (1Gbit LAN connection) is visible on iPhone and iPad as an Airplay client but connection cannot be established any more under 4.6.3.
The M10 shows the Airplay input icon but music is not playing.
I tried taking the M10 from power, restarting my router and reconnecting the M10 to power again - without any result.
The problem seems to be independant from iOS/iPadOS version as the devices run iOS18 and iPadOS 17.
What else can i try? Is it a known bug in 4.6.3?
Regards
Peter

further tests:
I also configured WiFi Connection to check whether its a problem with the LAN connection - same result.
Airplay to other devices works as usual.
TIDALconnect and SPOTIFYconnect work as usual.

I also did a complete factory reset but that did not solve the problem.