Originally Posted by tabetha

It sounds as though it has a sticky linkage, that is not moving fully, this will be on the door lock module on these where it gets it lock unlock signal from to work the other side.
It's quite common on a lot of cars for these to stick, when they don't reach full travel they rest in the mid position between lock unlock so you get one trying to unlock while the other tries to lock.
Usually just a good clean off in the lcok mechanism has it all working ok again, but DON'T grease the lock with ordinary grease as it attracts dirt etc, just use white parrafin grease, or silicone grease.
tabetha