The tip is much appreciated. I really *really* feel that the front passenger door lock mechanism isn't standard issue. I can engage the central locking system by pushing the button down whether the front passenger door is open or closed. Faulty is one thing, but it seems to do things that a standard lock can't be made to do. I only do this with the engine off. The driver's side works as it should per the manual.
I also feel that there is a physical barrier in the key hole preventing locking the door. It's nowhere near freezing in this area. The resistance doesn't feel like friction, it feels like a brick wall.