Central Lock Issue - Random unlocking/locking/unlocking

[Cruisin']

Hi,
my '97 GMC has been giving me a bit of grief of late, electrical and mechanical...
The current issue is the central locking system.
I recently had a new passenger door mechanism fitted, as it wouldn't open from the inside.
Over the last week, both the door locking mechanisms have been randomly unlocking, on and off several times, then again a few hours later, day in day out.. for the last few days.
I have had 2 flat batteries over the last few months and was wondering if it's a case of buy a new battery...???
Or, is it something else doing this??

Has me beat...
Anyone experienced this or know how to fix it?
Any help would be appreciated.

First it was the indicators and interior lights randomly going off (I just pulled the fuse) this was ages ago and yet to sort that as the truck was my daily work transport.

Then the aircon actuator linkage fell apart, I am yet to sort that as I can't reach easily enough up under the dash to put it back together... I will work on that... almost need 3 hands..

I now have my other work vehicle fixed as a back up.

Any pointers or ideas would be greatly appreciated.

Cheers,
David