Center Audio Channel dropout

I lose the signal to my center speaker periodically during live and recording playback. I've noticed it on CBS, but not other channels. Sometimes the commercials lose it, but not the programs; sometimes one commercial loses it while another doesn't. Now the programming is losing it.

A search shows this was a big topic in the Premiere era. But there is no recent discussion I could find.

I'm at a loss to identify the source of the problem, but it only started happening recently, after I changed to Roamio.

Any suggestions?