I’d be really tempted to reboot the TV….or check first for updates to the TV, and apply them, then reboot it by unplugging the TV from the wall for five minutes.  Unfortunately, most TVs don’t normally reboot their OS without actually unplugging them. Time varies, due to the need for capacitors to unload, but five minutes should do it.

However, if that doesn’t fix the issue, the next time the sound disappears, submit a system diagnostic, and call Sonos Support to discuss it. This does not happen on either of the two Arcs I have. Both connected to Vizio TV’s of various vintage. 

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network. 

I usually don’t comment on Sonos Firmware builds as most issues are acknowledged very quickly with a fix. That said I found I had two Arc’s with bonded sub and surrounds as Home Theaters  (HT) that seemed not to like the most recent update when performed globally.

I resolved the issue by unplugging all components in the respective HT’s including the Arc’s. I proceeded to update each Arc individually and then plug-in the associated components and let them come back. I then ran the update a second time for the other components. Knock on wood my system is behaving as it should.

NOTE:

Bear in mind that my solution is a one-off and may not work for your setup. Furthermore, it is not an official Sonos fix. 

Odd. I didn’t have any issue with my Arcs...but perhaps it has to do with other network topology things? 

It could also be a CEC problem. Have you tried to turn it off on all devices or use a HDMI NON-CEC-adapter? That could also solve the problem. Did the trick for me with arc/Samsung 

Hmm, This only happens maybe every 50 hours, but today I notic the hdmi cable wasn’t 100% in the socket, so hopefully that was the problem. I’m going to be a bit more patient. Maybe this one was on me. Time will tell.