Central locking problem..

[ThePistonHead]

I have read all the threads about central locking actuator failures but just wanted to see if anyone knew anything about my particular case which is a bit different to anything i've read.

When you press unlock from keypad, the drivers side knob will rise 1cm then fall back down.

Once you open it manually, then attempt to lock the door one of the following will occur:

Either both drivers front and drivers rear will remain open

or

Only drivers rear will remain open

or

None will lock at all.

Have pulled apart the driver's side rear door actuator and it seemed fine, cog still in tact and motor works when tested with 12V.

Although i don't expect much.. any body have any clues??