Exactly! Great advice - could be feedback via the HDMI cable - maybe try a different inputIf you swap Joeys (move the Joey with the problem to another TV, and put the Joey from that TV on the 4K TV instead) and the problem stays with the 4K TV, then it is some kind of compatibility issue between the Joey and your TV. If the problem stays with the Joey, causing problems on the other TV, then it is a bad Joey. (Or, as HipKat said, it could be a problem with the cabling to that room, causing the problem with the 4K TV.)