Its a right pisser as I always need to check the doors after locking ! them.
The two front doors will lock but the two rear one alternatly or together (no real pattern) dont intermittently. I also see an intermittent problem where if you lock the drivers door (while driving ) from the inside (obviously) it takes several minutes for the other doors to respond. Usually you forget about it and then get suprised by the other doors locking .
Im fairly certain its a voltage issue and most likely some earth circuit corrosion. It also likely to be the solenoids in the doors themselves or comnbination thereof. I remember reading about this , that if you pull them apart and clean contacts etc they apparently fucntion as good as new.
I have had this problem with my VP Calais. The left hand rear door would not lock or unlock intermittently. Sometimes you were unable to push down the lock button either. After checking the wiring inside the door, I found where the the loom plugs in to the locking mechanism was loose. I removed the plug, tightenned the terminals, plugged it back in and have had no further problems.
