i think the edge not working is the clue to work on, what would keep the edge from activating? I would think that the car does not think it is in the door zone, or as galaxy points out, maybe it is doing a slight relevel, and since you have no pre opening, that is shutting of the door open circuit. what ever the problem is, if you are lucky, you could monitor the DOI flag as vic has said, and catch it going off, but if it is really intermittent, that could prove to be a little tedious. why don't you try forcing the car to do a relevel as the doors are opening, and see what happens, also maybe simulate a loss of door zone as the doors are opening to see if you can simulate the problem. I would think if the door open limit failed at the halfway point, then the door would stop, and the door timer would begin, then it would close as normal. as far as the door close limit being open, causing the detector edge to become inoperative, i would test this. simulate a detector edge input when the doors are fully closed to see if they will open. some cars will open the doors if you break that beam when the doors are close. we used to open some doors by sliding a piece of paper in the door to block the edge, to get it to open at secure floors, where a pick was not working. good luck sounds like a good one