locks not remotely interested

hi techy type query this one.. i have a '95 disco 300 tdi which has an annoying problem with the remote central locking in as much as the drivers door locks with the remote as do the other doors, however within a few seconds the door lock button jumps straight back up and if not locked with the key or unlocked with the remote the alarm will go off.
if i lock the car with the key in the drivers door lock all is well and i just have to remember to unlock the car via the remote in order to avoid setting the alarm off. i tried changing the solenoid for a known good item but there was no difference.
i could just carry on locking with the key but miss the convenience of the remote facility
any thoughts gratefully recieved

does locking it with the key take any extra force on the drivers side? could there be something sticky that would be pulling against the solenoid (which isnt amazingly strong) so when the solenoid locks the door it is being unlocked again? using the key may be overcoming this.

is all the wiring ok, all earths ok? iirc the central locking works from a negative pulse so a bad earth may prevent the solenoid in that door working correctly so it'll unlock itsself.

not 100% sure on the answer an im sure somebody will be along soon with the right solution, but there the things i'd be checking 1st

the lock doesn't seem overly stiff in operation but i've got some graphite grease so i'll take the door card off over the weekend and try giving it a squirt or two of that.. i need the card off to grease the window mech anyway as i replaced it last week and just now remembered that i never greased the runners up ..... oops

while its off then check the operation of the rods that operate the lock.

Take the drivers door card off, locate the acuator and undo the fixiing screws slightly and readjust the acuator just a milimeter or two, thats all that's needed.