It's been some time since I looked at any of these controllers. On a unit this old I would go over it with a fine toothed comb. First I would check all your door locks. I would run the length of the shaft on inspect and check my clearances. If your clearances are good, how do the contacts look? If they are worn I would replace them. Second, Look at why your DPC is off when coming into the terminal floor.
As far as running and not allowing the doors to open, all the swift cars I worked on had a toggle switch for that purpose.
