For months the TOSLINK connection worked fine, then we discovered that both the Sony and Sonos Volume controls were active and sort of in series. The cable box Volume control counted as a Sonos Volume control. The customer could get into a situation where the Sonos Volume was max, yet there was very little system output. The Sony audio output seemed to be fixed, but there was a control interaction. In some respects it seemed as if the Sony Volume control was actually messing with the Sonos Volume Limit.

I'm not sure what happened to cause this. Anyway, I updated both the Sony and Sonos. The Sony updated twice. I was then able to go back to the eARC connection and use IR commands from the Cable box to control BEAM Volume and everything has been working OK. The customer can use both the Sony TV and Cable box remotes for Volume control and they don't interact destructively.

Do I feel all warm and fuzzy? No, but the system as been working well for several weeks.