Ford Windstar door lock motor

I have successfully installed my alarm/remote-starter/keyless-entry in my 98 Windstar.

Now the problem is that the driver's door lock motor is not working well. When you press the lock/unlock button (or when I act it with the remote) it sometimes open, it never closes, and usually it does nothing, it starts to move but fails to change position.

Is this likely a mechanical problem with the rods (maybe requiring lubrication) or is it a motor problem ? Any help ?

It has nothing to do with the alarm.

Before installing it did the same. It opens perfectly with the key. But when using both lock/unlock buttons (left and right door) the driver's lock moves but doesn't change state.

I tried lubricating the motor and the rods in general, but not being able to look inside the door I might be missing something. The other chance is that there is something wrong with the motor.