I wouldn’t think so, no, but it does suggest that something is sending a volume down, or mute message to your PLAYBASE . Since the PLAYBASE is connected to your TV via optical, it has no way of sending a volume command back to the TV. First, I’d make sure the optical output on the TV set was in ‘Fixed’ mode, not variable. Then I’d double check your remotes (both the TV’s and the Apple TV to ensure neither of them are sending an errant command to the PLAYBASE, and if no joy there, I’d 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. Especially if the PLAYBASE is receiving a mute command. 

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 network and Sonos system.