An opening on the top of the lift was large enough for the inspection door. We
assume that the person didn't set in the inspection door completely in the right
place, and the door was shifted a little from the opening. Therefore, we assume
that the door could come off when force was applied. Normally, the person
connect a fall protection harness to a fall protection anchor before his work, but
he didn't connect the harness this time, because he was moving to the next lift.