Hi Bracken.
Just looked at a similar issue on my 4.6HSE P38 earlier today and I 'located' the area by tapping/slapping each of the doors, in turn, and the tailgate and I noted that the central locking would cycle every time I slapped the passenger external door skin.
Whipping the door card is simply a matter of removing three screws, (one in the Door Catch Release Lever), and two in the Arm Rest but my 'problem' was obviously the result of the previous owners quick fix as it was a loose female spade connector that was being used to mate with the original door switch plug, (which had obviously been cut off previously).
I will solder my connection in order to make a professional repair, (that will never cause any future problems), but I will replace the plug if I ever have to replace the Switch.
Another 'job' that can be ticked off the, long, list!