You do have a very odd condition! This series uses a newer display system which places part of the displays logic (T-CON) within the uppercase as you can see here
But this doesn’t get into the drawing of the objects! As you can see the issue is not a global wash of a color or pattern (bars or noise). You have artifacts within a given object (a line in this case) The object is a drawn property based on Quick Draw the color within the line at different points is oscillating the background is not altering its color (either horizontally or vertically from the artifact in any direction)
This is a failure within the main logic boards graphics engine which composes the image and then tells the T-CON what is needed (not a display unit issue).
This will require a new logic board. I’m not sure I understand the persons logic not to come to this conclusion just looking at the info you supplied here.