From what I can work out from hearing various stories, the PIA aircraft was parked on Stand 13 or 14, during the offload an Interserve ambulift (which has been on station about a week) was going to take a wheelchair passenger through door R1.
Except it was positioned too far right, so when the ambulift body was raised it clipped the front cargo door causing a failure of the hydraulics, and the door slammed shut.
AFAIK the cargo door is no longer flush with the cargo door, as the resultant force of door falling has caused ripples in the skin, no idea about the hydraulics.