PlaySound or playStream on a AUNA KR200 Kitchen Radio

im trying to send sound to a notify audio sink. One good option would be our kitchen radio. The UI features of the binding are working well with this device.
Did anyone get managed to playSound or playStream on a Frontier Silicon Radio, espacially the AUNA KR200? When I send playSound() the radio tries playing but always shows “buffering”. No chance do get success.

I am running openHab 3.3.0 in Docker on a Synology NAS.