Shady
3
Either a bad cable/interference or a bad board/input on the TV itself
I remember seeing your setup, how long is the HDMI cable run? Have you added anything new since the initial setup?
The fact that its not saving the setting is why I am suspicious of it being a bad board… Will it save other changed settings?
Try putting the cable in a different input on the TV, also try using another device, narrow it down