Passenger door lock is stuck

My 93 Ramcharger has power locks which my mother insists on using manually. Her lock always gets stuck when she does that. Usually I'm able to get it to work by getting out and jiggling the key about inside the lock. I can feel something resisting, then it lets go and works properly until she pulls the lock up manually again, which she did today. Now the lock is stuck somewhere between locked and unlocked, and the door won't open from the outside or inside. The driver's side works fine. Any suggestions as to what the problem might be and how to fix it? Thanks.