You get diff wind up when you have had it in diff lock and one of the axles are spinning free, then the lock will wind up and kick in. There are 2 ways of getting it off, 1 is to drive forward on a good surface, not wheel spinning, and if that does not work then you need to reverse for 20-30meters to unwind it.
I would be worried about the light, make sure you can still mae it light and the garage has not just unpluged it or something.