The door full open contact is at the rear of the lower slide rail, there is a curved shaped pivot that presses against the microswitch.
Its common for the pivot to stick but that should cause the door to open and immediately close.
The pins in the door jamb act act as a closed switch on contact.
Pretty good info and working description of the system on servicebox online.
Think the switch info is in data in the bsi as well as the door controllers.
Ray