Central locking.......

Intermittently my car will lock as soon as I unlock it, it doesn't
happen the other way round. It's also been trouble free for the past
month after being intermittent for the previous 6.... I was thinking
this is different to the usual "car still thinks there's a door open"
problem as it's the opposite of the "car unlocks when I try and lock it"
problem I've seen when googling. Anybody any idea what could be causing
this? Related to this (probably) is the fact that when I lock the car I
can hear a "brrrrrbrrrrbrrrbrrrrbrrr" noise from the drivers door for
around 2-3 seconds after the locks go down. Sounds a bit to me like an
electric motor trying to do something, could I have a dodgy actuator in
the drivers door? Usually if it's in "bounce" mode I can stop it by
manually using the key in the lock rather than the remote.
I've not taken the trim off yet to have a look, and don't really know
what to look for apart from dirty contacts and mechanisms.

Anybody help, or point me towards a source of help?