2006 Hyundai Elantra. All of a sudden, the front passenger door lock is stuck. The remote key fob works for the other doors, but not this door. Also, when trying to unlock it manually from the inside, the switch won't budge. It's definitely stuck and I know better than to force it. From the outside using a key, it will work, but the key turns with quite a bit of resistance and the door will open if I pull on the outside handle while the key is turned and held in the turned position. Any ideas as to the likely culprit?