So I found a way to minimize the issue, and that was to "hide" all of the other inputs besides the one I use the most in the HDMI setup menu. It still occasionally likes to try to switch the source itself, but does not have one to go to so instead the screen just goes black for about 5 seconds and then returns to the original source. I tried unplugging the unit for a while and also covering the sensor to no avail. Need to contact Denon probably but without the warranty I'm not sure it's worth the effort.
