I've had a problem with the door lock on a 2001 Galant: sometimes one particular door does not lock or unlock with the other doors. My theory is that there is some mechanical resistance which the solenoid does not overcome. My temporary solution is to use the key on that particular door for a few days so that the key does the mechanical work, and loosens the mechanism a little. As expected, it improves things for a while.
I apologise, because a temporary solution often makes the problem less urgent, and so it is never fixed properly.