Samsung TV no picture but sound there, except for apps. What is the problem?

With my Samsung TV (UE55H6470) the picture is completely black, if you look closely you can easily see the smart apps and if I then go to Netflix or Amazon Prime, the picture is fully there again.

software or hardware error?

How is it with TV channels?

The backlight is obviously spinning, reset it to the factory settings

https://praxistipps.chip.de/...ehts_42945

Yes, with normal TV watching the picture goes on and off and on and off.

I already did the hard reset, but unfortunately without success