MPC 4000 Display not working, Replaced Display and Cable

So I replaced both my MPC 4000 display (TWICE!) and the FPC cable attached to the display PCB and the I/O PCB and there are still lines on the screen. What could this mean? is the display PCB faulty? Is the port where you attach the FPC cable to the I/O board faulty? I am at a loss here. It can't be the display itself because I have replaced it twice and the lines are exactly the same and It can't be the cable because nothing changed when I replaced it.

Lines on the screen are usually a fault with the connections in the ribbon cable,or the socket where the ribbon cable plugs in over time they become less efficient,mine used to have flickering lines but once the unit had warmed up for a while they seemed to disappear with a few twists of the contrast knob, but over the years this had little effect and the lines were always present and it became annoying.

replacing the whole screen real estate that should have sorted it if it was the screen itself, which in your case points to the same issue i had and it wasn't the screen itself but the connections, you have to be careful with the ribbon cable tips as they can be damaged if not fitted carefully

I got an electronics friend of mine to realign and clean, and tin the tips on the connections of both the ribbon cable and the socket and it sorted the issue.