There's a couple of initial suggestions. First, go in to the audio settings for the Samsung, and make sure it is locked down to Dolby Digital. Look for the settings area in the TV's settings for software updates, and make sure that the TV is running the latest version of the software. My understanding is that Samsung has published new data in the last several weeks, but I don't know if that update is applicable to your particular TV set.
Then go in to the audio settings for the Time Warner box, and the Apple TV. Set both of them to Dolby Digital as well. Make sure the Apple TV is up to date while you're poking around in its settings area, but that's not critical, I think, But as long as you're there, might as well double check that it's running the most recent version of iOS for TV.
Then I'd be looking at the connection of the optical cable, since it's when it is in use that you seem to be having an issue. Make sure it is properly seated in the connection at both ends, in the TV and in the PLAYBAR.
Shoot, while I'm thinking about it, make sure you're running the latest version of the Sonos software, both on the controller and the speakers. In the controller app's settings area, click on "online updates" to be sure.
I *think* this regimen should hit the problem you're experiencing, but in case it doesn't, I'd recommend that within 10 minutes of one of these volume changes, you
submit a system diagnostic, and
call in to Sonos to discuss.
