The ribbon cable connecting to the display board is prone to sharp bending at the connection point, causing intermittent displays. I am experiencing this with a new processor, where the display only works half-way open, then goes out when open or closed. I had another processor where the ribbon cable tried to pull out, when opening/closing the display door. As a suggestion, could the ribbon cable be glued down with hot glue or silicone?
As an update, I have replaced the ribbon cables in 2 processors successfully. I found that in both cases, the cable was bent sharply at both ends, and sharply bent in 2 places in the middle. When installing the new cable, do not crease the cable. It is easier to remove the hard drive to connect the ribbon onto the main board without creasing the ribbon. Ensure the cable can move freely through the front opening and leave a bit extra out the front. At the display board, the ribbon will automatically be creased after the door is closed the first time, but it will tolerate the one time. The key is to not flex the crease. As for gluing, I believe this would prevent the door from closing properly due to the tight space.