central lock problem

[obeone]

When i lock the drivers door with my key the drivers door and boot lock but passenger side doesnt.The passenger door will open by key on its own.i jhave taken the door trim off and watched and the button does move down when central locking operates but then goes back up.I have replaced the door electronic box thing but no difference so its not the door solenoid thngie.
Any ideas?

[SAXO8VYO]

mine does this sometimes i just put the fault down to it being french mate lol