I've been stressing about this. My tv would go dark only if the picture was dark or tv seen was at night so I would crop the picture and have a steady on background on the section that would go dark.
The other strange thing is that in initial setup mode the TV would stay on with perfect picture forever, but when done it would go dark again blank u can see picture only by shining a torch onto the screen and also barley.
But for the past week my picture has returned I no longer have to crop the screen everything is as it should be.
The issue was power, we unplugged alot electronics changed the multiplug and immediately saw a difference, check power supply to the socket as well