You have damage/poor connection to that part of the LCD. Replacing the LCD would solve the problem.
Once you have the front bezel off, & the LCD removed from the cover there's a manufacturers' sticker with part number on the back you could use to find a replacement screen.
You might find a working display from a laptop with logic board damage (wouldn't have to be the same color any 3,1 display would work.
Only you know how much money you wan to put in this machine.
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