Issues with resolution Apple TV 4K after TVOS update 14.5

Since I've ungrade my ATV to 14.5 I have had issues with the resolution. It won't appear now through my AV reciever. I've had to use it in another TV and changed it to 576p. I tried this in my reciever but when I try to change back my screen goes black. It was working perfectly before this update. Also the ATV is now stuck on 576p and when I try to change it to any other resolution it gives me an error and stays on 576p. What a nightmare.