Thanks gonk,
Hadn't thought to ask the cable company about filtering, but have read other places that cable companies have done similar things. I know of companies coming in and adding a signal booster to end users' homes so the company can make sure the equipment is installed correctly and thus prevent cable system degradation or RF noise generation. I do know they're on the hook with the FCC for spurious RF noise generation in communication, radio, and TV spectrums.

Steve at Outlaw Audio was wondering if a potential voltage drop was the culprit here as well. Just checked my battery backup configuration and found it had reverted to defaults, so shifts due to voltage were not as tight as I'd set before. Current voltage is 116 volts (cooler weather today), so during the heat voltage was most likely less. If I remember correctly Steve mentioned 110 was kind of a critical floor. So your idea about unit running hotter may be applicable. Tracking the temp above the unit during hot weather might be worthwhile.

So will see what happens next time outside temps get up there.

Cheers, Jim