Thanks for the pointing. Would've have noticed it without that.
Unplug it for about 30 seconds and plug it back in. Most new TVs don't actually turn all the way off when you hit the power button.
Restart then check and see if u have update for the box. If u have device preferences go to display and check out the settings to see what settings work best for your tv.
It could be the HDR confusing the TV. Does it happen on non HDR content?
Update Netflix if possible, hard restart, clear Netflix cache/data, try content of different & same video quality (eg. HDR, non-HDR, non-4K) and see if issue is just on HDR and/or 4K.
Consider if any settings changes had occurred before this started happening.
What type of Android TV box is this?
It's because the video View is glitching. That is a specific part of the application that renders the video. All other stuff on the screen are built from other types of views and are layered on top of the video view. That's why the screen looks normal except for the video.
Hard restarting might do the trick. I too have this issue from time to time. A restart often helps.