no harm in taking door card off, under a 5minute job, just to see if the connector block leading into the motor is loose? or testing it!!!
just i think you should be keeping an eye out for "passanger side motor" from a micra or primera!
underneath the steering column is a black box, this is the central locking main control unit! see if any of those wires are loose!!
also sit inside the car, somewhere, where its quiet. close all the doors. from inside lock the drivers door!! you should hear a "tick" from the unit under the steering column! and try the same with the passanger, they should both "tick"!!!
hope this helps