As I mentioned earlier, the Sprinter we bought is a fantastic vehicle thus far, but has some minor niggling issues that while not show-stoppers, I sure would like to fix them. One of them is the door lock system - there's a fault in one of the rear doors, which manifests itself as the doors locking then unlocking when you push "Lock" on the key fob. When you hit "lock" a second time, the doors lock, unlock, then finally lock again.
Some of them.
So I set about figuring out why that is, and it's opened up a can of worms. It appears as though the door lock actuator on the passenger side sliding door is disconnected, and the two sets of wires that go to the copper contacts appear to be identical, with neither pair of colors matching up to what the service manual says they ought to be.
The situation is worse in the rear "barn" doors - there appears to be no door lock actuator at all. The lack of an actuator and the fact that the door interlock switch appears to be completely disconnected most likely explains the spotty key fob behavior, but it'll take a bit more research to figure out what's actually going on.