Part time Power Door Locks

Our 99 Montero Sport has started having part time power door locks. Sometimes they work, sometimes they don't. This includes when using the alarm remote (factory) and the buttons on the doors. Heck, sometimes, when the doors are locked and I reach over to try and unlock a door it fights to stay locked and I have to hold the lock switch until whoever pulls the handle to open the door. This affliction includes all 4 doors and the rear hatch door.
I'm pretty good with cars and trucks, but most of my experience is on vehicles before the auto-door lock was a common feature. I have a feeling there's a relay or controller that is spazzing out, but I have no idea where to look or what to look for. Any info on where/what to look for or how to fix would be greatly appreciated.

I have a 94, that does the same thing. My preacher says,...It's the "Devil"....

Starting to think that Montero is Japanese for that same word!!

try maybe the mechanism for the central door locking...maybe something there's intermittently shorting out.