It looks like patches. Maybe if the TV has...what do you call it, local lighting? The brightness is just right to trip those?
searches
Local dimming.
I wouldn't think that it'd be so visible, but it sounds like it's at least possible to produce similar artifacts on some televisions.
2019 QLED - Local Dimming unsable on HDR content - Brightness flickering in gray/dark scenes
This is not limited to HDR I believe but more pronounced while watching HDR content. The issue is that the local dimming seems to be unsure what brightness to use causing the brightness to flicker. This happens especially on grey or darker background walls in movies and so on. The biggest issue is, that it causes multiple areas on the screen to flicker. It's a bit difficult to film, because scenes change fast and the camera is masking this problem a bit. But I could "simulate" this issue in this video. Watch the dark horizontal band starting from the middle of the screen to move up after the top timer bar disappears. The bar disappears in less than 1 second yet it affects half the screen for a whole ~3 seconds. It's like a shadow or ghosting effect.
https://www.youtube.com/watch?v=Kym5aHsYaEU
Now imagine this happening in every dark scene when there is something moving and the whole area left and right is affected by it. It's a constant flicker in those areas. It's not limited to the light source changing, meaning this isn't like blooming when you use subtitles. This stops when I pause the movie or when there is absolutely no movement/change in the scene or when I enable Game Mode, meaning when Local Dimming is turned off.
It's so distracting that I can't really watch anything anymore without looking for it. I noticed this a few times after buying this TV but I rarely noticed it after that. Now it's suddenly so extreme that I can not watch darker movies because it's constantly flickering.
Everything from ECO mode to Intelligent Mode, Auto Brightness etc is OFF!
If your TV has local dimming, maybe try disabling it?