My interior door lock has stopped working 99 Chevy Silverado. It unlocks manually using the key in the outside door lock, but does not work with either driver or passenger interior unlock/lock button. Both buttons operate the passenger lock just fine. When pressing the lock button the lock will move slightly as if it wants to close, but when pressing the unlock button lock is completely unresponsive. Any advice what to replace or check please advise

Also just to throw it in my headlights are alwAys on, which makes me think my auto dash sensor has gone bad, anything else I should check? Thanks for the replies