FYI - In diagnosing if a stuttering, and quality problem is the Tivo or the network, if you rewind the content prior to the when the stuttering, flicker or audio drops and it still occurs at the same place/time then it's a defect in the recording not the network transport.
I can't say for other cable providers but I have high compression and signal lost with my cable provider, it down right wrong when they claim"HD" crystal clear channels yet in fact my HD content is terrible. I'm on suggesting necessarily such is always the case to blame the cable company but that is what comes to mind at least in my situation.
With that, I'm seeing the same audio drop out too on my Roamios when there is a tuner change, before and after the last update and as mentioned, Toslink optical doesn't appear affected by this but rather audio over HDMI. Doesn't always occur often, just enough to notice. Sometimes the audio drop is short, other times it's more than a second or two, as habit the first thing I do is press the up volume button but that doesn't help of course.
TiVo Roamio Pro
TiVo Roamio Plus (3tb)
TiVo Mini (three)