I'm fairly certain this is what is happening ... When the 976 powers on, the Apple TV also powers on and if the 976 input is set to the DVD player or the PS4, the Apple TV turns off after 15 minutes which causes the 976 to turn off. When I unplug the HDMI cable from the Apple TV, I do not see this problem. I set the HDMI Control option on the 976 to off and the problem goes away.