I highly doubt the LCD is causing this problem. It is probably related to the customer trying to replace it himself. He may have knocked off one of the surface-mount components near the FPC connectors (battery, LCD, Digi, FCAM).
This logic board needs to be inspected under a microscope or 10X loupe.
Depending on what you find, it may need to be repaired by someone who can do micro-soldering.
Can you post pictures?