Do you know how to fix the white line down the side of an iPhone x?
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That’s very likely a screen replacement.

Screens work by displaying dots on an x and y axis (sort of like the game Battleship). Each dot has a set of coordinates. When one pixel dies, it’s barely noticeable. You may see a small dot not the same color as the others. But when you see an entire line going across a display, that usually means the whole line is not getting the information and therefore are just showing one color. This is not solvable by software or a simple reset. This is usually a hardware failure.