So the display flashes High Heat with the fans running and automatically lowers my volume from just moderate listening levels. What's strange is that it only happens with my cable box connected to my AVR and not with anything else. Whats even stranger is that In just experimenting with settings, when I raised my crossover from 80hz to 100hz, it solved the problem. Why just with the cable box(Verizon FIOS) does this happen??
This is a strange one. However I suspect the fault does lie with your FIOS box. I suspect it has a suprasonic oscillation, most likely due to a fault in design. I suspect also that your Pioneer does not block suprasonic hash at the input, which it should. Companies just have to shave a few cents to get that edge, don't they?
The power draw of the receiver is reduced when you up the crossover point and stops thermal protection cutting in.
I suspect your TV may block it, and so connecting the FIOS box to the TV and using eARC may well solve your problem.
My hunch is you are suffering from the interactions of at least a couple of instances of poor design.
Let us know if using the TV eARC route solves the problem.