I have had a very similar problem with mine but only when actually in it - not overnight. It got to the stage that the N/S rear door locked itself and could not be opened at all! The car was under warranty and the dealer replaced the wiring loom to sort it. This happened about 18 months ago and it has just started happening again. I covered the contacts on the door to stop it locking permanently and now pull the lock up and down. This seemed to have stopped this happening however, this morning the locks started jumping up and down again
Paul R
January 2009