Widevine L1 Bug?
I had the same issue on my new Sony Tv had to replace some motherboard which I payed almost 500$ bucks for it.
The tv is behaving like that on the live channels. So it is not a video playing in a player or a different source, as you can see in the video the black screen apears on cable television, all the tv chanells are black with sound.
I was refering that I don’t use any player app or have a box from the cable company, the only thing I have is a card inserted, the name is CI+ card, not cdmi.
Thats a player issue. Not a TV issue. Display is working fine.
Looks like a codec issue. I would just use a Chromecast with Google TV and be done with it. Most of the built in TV smart features are crap anyway in comparison. And even the decent ones are slow and laggy compared to Chromecast.