Android: suddenly, can no more stream radio and use other app (for instance e-mail) simultaneously

It's almost like having too many devices connected to your wifi will cause a decrease in speed.

I'm glad you figured it out and this will help other people.

Mark your post as correct answer so if someone has this issue they will see this thread they may find a fix.

I am surprised that the developers did not provide this "trick" to the support staff. In fact, I am not surprised.

Sometimes deleting devices you're no longer using with your Bluetooth connection seems to help, I don't have many devices I connect to.

Addition: I just tried to reset the Bluetooth cache and delete the data; the option was greyed out.

The only remaining option is too destructive: resetting Wifi, mobile and Bluetooth

Thanks for the answers. I am using SE 20 5G and tried all possibilities using the battery parameters to no avail. Actually, this happens when I use a Bluetooth device to listen to the streaming app. It looks that there was a recent modification (bug? careless "improvement" somewhere causing problem elsewhere?). I swear I did not drop the phone in my bathtub!

I'm streaming radio right now with no issues on a Pixel 6 using the station app.

 The only time I lose connection is when I open an app with Bluetooth permission then the streaming stops.

Android 12 and 13 have changed how apps in the background are handled.  Depending on your device, there might be a high performance mode or an option to prevent an app from being put to sleep when it isn't in the foreground.  On my s23 Ultra as an example.  individual apps can be controlled under Apps, Battery.  Turning off optimizing for battery usage keeps the app always working whether it is the active app or open in the background.  This can slightly increase battery use.