Strange that is is stuck locked. I would do as Eddy said. Jack up the rear, and put it on jackstands. jiggy the wheels back and forth, and see if it is ACTUALLY locked, and not just indicating that it is locked. If it is actually locked, I'd rap a hammer on the housing while someone jiggi'ed the wheels back and forth.

The locker is spring loaded so that when it gets no air pressure, it automatically retracts and unlocks.

87 Raider 4D56td v5MT1
31's..Basically Stock