I have same experience with this problem, i had bought this imac 24" base model on 2021 November in Yogyakarta Indonesia, and have this problem like this: and after I bring to Authorized Apple Service Provider in my town, they diagnosed that my display must be broken and need to replace, they charges me around 810$ (13million IDR) so I canceled it because it's not worth it, after I bring back and turn it On again on my home, the screen only have tiny horizontal and vertical lines on the corner like this: does anyone have experience like this before? or is it because the cable that connected the display and logic board inside?