The point I am making is this idiot passenger forced the door back open when it was closing so his mate could get on. The air pressure to close the sliding doors on a 321 is not insignificant so he would have had to put a considerable amount of force on the door to hold it open again. But how many times do you see passengers attempting to board as the doors are closing even though there are clear signs everywhere saying do not attempt to board as the doors are closing. The doors on a 321 are fine and work perfectly well day in day out its only really when you get idiots trying to interfere with them that you start getting faults.