I recently started having this problem on Roku Express 4K+, at various times
1. The top 4/5 of the screen is darker and flickers (except a narrow band at the bottom)
2. Ghost images from a previous frame stay on screen, creating a double exposure effect
3. White lines run from top to bottom (they appear to be aligned to text or graphics eg the Disney+ logo)
It’s not the TV, as a Chromecast device doesn’t have this issue. In fact when I switch to the chromecast port, the ghost lines disappear (only to reappear after a while when I switch back to Roku)
Any clues anyone?