I have seen similar vertical line on an EX90 LCD screen, but this is first time I get to see somebody report such a failure on the touch panel.
I think the principle is the same. Screen matrix of rows/columns has a defective column of pixels.
Hardware issue I would say.
Interesting fact here is that this was not an issue when the unit was unboxed out of the factory. It just appeared after some time.
I am still inclined to say this is hardware error.
In the case of the bad LCD, when we applied "light" pressure on the top/bottom of the vertical line, the vertical line sometimes went away, but re-appeared afterwards. You could try same on your touch panel.
I have the same issue on two devices, MX200 G1 and EX90, funny thing is that it disapears on MX200 after a while, I think it might be a firmware or software.