Wide Vertical Bar Down The Display - Have you seen this before?

I think your thinking about the backlight cable pair being difficult.

I'm referring to the single flex cable, which is an easy fix - I've put in a few before, however, in those cases the screen had several vertical lines. I've just not came across one with a single wide bar down one side.

MacBook Pro 15" Retina (Late 2016-2019) Display Cable

@Country Computer Service That part never breaks, if it did, the screen will be just off or randomly snowflakes/artifacts. The failure type you have is clearly analog in nature, something about row/column traces broken.

So, you've seen this exact same pattern before? Just a single grey bar? I'm trying to rule out the T-CON Flex Board Cable, before the timing controller.

@Country Computer Service - Yes in all of the TouchBar models as the T-CON overheats due to its placement! Often we see the horizontal over/under scan. which creates black bars at the top and bottom. While not as common the vertical sync can also slip so the buffers data is not fully wiped.

The displays data cable (the short one between the logic board and the T-CON) just doesn't fail, the only exception would be a liquid spill getting into the connector interface board or T-CON. And the displays T-CON to LCD cables wouldn't cause this effect.