I’m not sure if there is a completely automatic solution. How are you stopping the music? Is the TV still powered while you are listening to music?

Thanks, much appreciated.  The fix varies. I stop or pause streaming music. Easiest fix is off/on the autoplay toggle in Sonos app but it’s not 100 % foolproof.  If nothing else works I reboot my Motorola cable box, a guaranteed fix, but a 2-minute waiting process.

Turning the TV off before stopping music (if I think of it) and then restarting TV afterwards works too.…

I suspect that you are correct about no automatic switch back to TV audio after stopping or pausing music..

The cable box restart must trigger something on the CEC (Consumer Electronics Control) bus. CEC allows boxes to communicate events such as ON, OFF, Volume UP, input select, etc. over the HDMI cables. Evidently, the cable box reboot convinces Arc to Autoplay. You should try changing inputs on the TV. It’s possible that this will trigger Autoplay. I don’t know if this will be more or less fuss for you compared to toggling Autoplay. You can also Browse music sources with the SONOS controller and select the TV.

A simple music Pause shouldn’t trigger Autoplay because this will generate complaints from users who want to Pause a track while they are on the phone.