It might be helpful, the next time it happens, to submit a system diagnostic within 10 minutes, and call Sonos Support to discuss it.
There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution. I’d certainly expect they might be able to tell you if this squawk is coming from the TV set.
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.
A couple of other things, I’d probably check the TV for updates, and then reboot it by unplugging it from the wall for 5 minutes, before plugging it back in.
There have been reported cases, albeit very few, of a cable box turning on to check for updates, which sends a signal to the TV, which passes it on to the Sonos. But generally speaking, your TV shouldn’t be passing any signal when it’s turned off.