So I have a Kia 2005 Optima, is in great condition and drives well and everything works just fine. However this morning the lock on the driver side stopped working. Even when I press the lock button the door remains unlocked. Every other door locks and unlocks without any problems. But the driver seat seems to have some problem, the lock on the side of the door which is supposed to move when you lock the door does not seem to be responding. What is the problem? How can it be fixed?