Apple tv 4k

Hi All.

I just replaced a A-TV3 with a new A-TV4k (2021). The following problem did not occur with A-TV3, so it has come with the change to 4k

When connecting a new IOS device to A-TV 4k, via airplay, the audio is missing. A restart of the A-TV makes the audio come.

For example; A-TV is playing from one of the build in apps. iPhone-A wants to connect and stream music, the phone connects but no audio although it appears on the iPhone as if it is connected and playing, restarting A-TV makes the audio from iPhone-A come through. Now iPhone-B wants to connect and stream music, iPhone-A disconnect and B connects, but there is no audio. After restarting A-TV audio from iPhone-B comes through.

Fun fact-1: If I instead of music stream a video, there is audio..... only when streaming music, the audio is missing.

Fun fact-2; in a different house I have another A-TV4k, at this one I have no issues. Everything works as expected when streaming.

Any idea what can be the root cause?

Thanks in advance.