On the DOOR the guide pins are just that, guides to stop damage to the pads. The top of the door is stopped from moving out by the guides until the stops have cleared the pad structure. Remember thare are no pressurisation loads on the DOOR at this point, the vent panel is open.
The DOOR is stopped from moving up by locking pins that are pelow the viewport between the second and third stops / pads.
It appears that on the PLUG there are no locking pins, just 4 bolts. Two apparently going through the guides and into the pins (near top of door) and two at the hinge / springs at the bottom of the door which I've seen no detail of.
Looking like the top bolts at least were not fitted. They would not be highly loaded, at most opposing the force of the lift springs.
There is however another possibility:
Some or all of the Stops / Pads were not adjusted correctly leaving the guide pins and locking bolts carrying presurisation loads leading to failure from low cycle fatigue.
EDIT: just found latest youtube info
This shows the bolts through the guide track and details of the lower bolts. Looks ike either all bolts were missing or the stops / pads were mis-adjuated causing pressurisation loads on the guides and guide pins.