I haven't had your year door apart before, but I'll bet it is similar to most others. The knob and handle use a separate rod from the actuator motor to connect to the lock. Since you say you hear that actuator and see slight movement, my first guess is the its rod has become bent and no longer has enough movement to engage the lock. My second guess is at each end of the rod it connects through plastic grommets. It might have dislodged from the connections or the grommets have broken. To find out what is really happening you will have to remove the inside panel and take a look.