@keta494 you pretty much did already everything that could be causing this issue, including a reset. The only other thing to do would be to change the screen. Sinced iFixit does not yet have a specific guide for this, use something like [https://www.youtube.com/watch?v=Ucffcaykga8|this video] Once you have your phone open, do check the ribbon cable as well as teh connector since we can't rule out issues on the main board. If a new display does not resolve this, then you'd be looking at circuit board issues. For that you will need the schematics, component layout as well as special tools etc.