driver side door lock stopped working

I recently cleaned the car. Now for some reason, one of the back door actuators, only goes have way down when locking, there fore the door remains unlocked. I have to manually push it all the way down to lock it. When I am in the car and open the locks with the switch, they all go up and unlock all four doors. But when I pushed lock button, the passenger rear door only goes down half way. What can be done? I already spent 250 dollars a piece about 50 thousand miles ago getting all four actuators replaced. I hate to spend another dime on it.