Problem: Our new LG G3 TV was turning off after 15 minutes when the HDMI switch is set to the Spectrum DVR. It worked fine when the HDMI switch is set to the Apple TV 4K. It seemed to be some sort of interaction between the TV and the DVR.
Googled several things. Various solutions presented. None worked.
Things we tried:
None of the above Googled solutions included multiple inputs through a switch. It turns out that the Apple TV 4K sleep timer was the issue. It was set for 15 minutes. Even though the switch box was set to the DVR, the HDMI-CEC settings of the Apple TV caused the TV to shut down when the (disconnected) Apple TV went to sleep. Somehow the Apple TV was communicating control even though the switch box was set to the DVR.