Duly noted Ernie.

I think next job I'm going to A/B test...

The next job I do has a bunch of CATV boxes in the same rack; two for distributed audio, and a bunch for distributed AV.

I might leave on the audio boxes all the time but power them on a fat UPS and see if I get any funny business.

Either way, both solutions (UPS, switching off) would hopefully solve the problem.

We gotta be really close here.