Recently I made an attempt at repairing a GG with a busted screen. Swapped it with another original screen but come to find it too had damage once I got it soldered to the board. No matter how much I cleaned the solder points on the ribbon cable I couldn't get all of them to solder in place. I decided to keep fiddling with it as I didn’t have anything to loose as both screens were damaged so I tried a few things to see what would result. On several occasions I was able to correct the thirds issue on the screen by reflowing solder points on the pcb where the ribbon cable connects. My colclusion is that various solder joints for whatever reason are "loose", not soldered properly, maybe even in the process of losing its connection. This can be a risky process as you may not get every connection soldered again without taking the entire screen off and removing the old solder and applying new to the motherboard. If you attempt it I suggest using a metal spudger to hold the ribbon cable down on the leads that you're attempting to reflow. With a wedge tip I was reflowing 4 or 5 connections at a time.