you got a lazy lock - known issue... happened to me in costa rica, rear left lock went asleep... by the time i got around to start working on it, the car was in russia, and all of a sudden, the lock started to work... but many misterious things had hapenned in russia - one of our SeaBees brought in a car with disconnected rear speaker, and when he got the car from the russian authorities, everything was working...

back to your issue - when you electronically lock or unlock the car, can you hear any attempts inside the door? i mean, you might need to clean up the crap out of you present lock and lubricate it...