It might be the output of the TV set that’s been reduced, although I’d be careful about over indexing on specific numbers.
What I might do is double check that the TV set is up to date on its firmware, then I’d reboot the TV by unplugging it from the wall for 5 minutes, then plugging it back in. You could, at the same time, reboot the Arc by unplugging it during that time period.
You can always submit a system diagnostic within 10 minutes of experiencing this problem, 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.
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.
Many thanks Bruce
V clear and constructive.