First thing I would do is check the TV for firmware updates, and then make sure the Apple TV was on the latest software as well. While you’ve checked the Sonos, it can only play what it is handed via the HDMI cable, so I’d double check the seating of that cable at both ends, double checking that you’ve used the Sonos supplied, or an HDMI 2.1 high speed cable.
Finally, if none of that makes a difference,I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it, being certain to tell them what source program you’re testing with.
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.
This could be an EDID (Extended Display Identification Data) spat where one end of the HDMI connection is not satisfied and forces a re-negotiation of the sound and picture formats shared between the devices. These are difficult to prove or deal with -- if this is the issue.
At this point we don’t know which box is at fault.
Some things to try:
Make sure that all of the HDMI cables are fully seated in their jacks. The plugs and sockets are not quite what you may be used to. A couple of the pins make contact after the others and these pins are important in the EDID process. If the plugs are not fully seated these pins might be making intermittent contact and forcing re-negotiation(s).
Unless this is a surround system, simplify the audio output format to PCM Stereo on all boxes (AppleTV and TV)
Rebooting all of the boxes is standard fare. In most cases a simple power removal will initiate the reboot. SAMSUNG TV’s will not reboot at this time. Keep the power removed for at least two minutes.
I’m not confident that any of the above will be the “magic bullet”, but they are easy to try.
The diagnostics will have some data to share.
