Actual issues with AirPlay 1 devices

[Andreas71]

Hi everyone. I have problems with  my iPhones to Play music on my old AirPlay 1 Pioneer Receiver. I can select the receiver, but the Output is still on my iPhone. I have the Problems on 2 different iOS Devices. iPhone 12/14.

The Receiver works for years without problems. And with my old iPad i have NO Problems to play the music via AirPlay on the Receiver. So i think the problem is in the App or in the iOS(16.5). 
What I have done so far:

restart/softreset IPhone.

Re-install Spotify App (using Spotify guideline)

restart Receiver.
Restart FRITZ!Box 

next Action is factory reset my iPhone and do a new Installation. 

Anyone here with the same Problems and maybe a solution?