I put up a page here to show the problem at the repair shop. If you put your device into landscape and zoom so the chessboard pattern fills the bottom of the screen and the top is white, the lines are very noticeable.

Since I first noticed the lines, I've now started noticing them everywhere, where there's something dark next to something light. Even just opening the vkbd in apps with white background in landscape view I see the lines fill the area above the vkbd.