E39 Driver side rear door lock inoperable
I have a 1998 523iSE (UK) and driver side rear door lock doesn't work using central locking. I can lock/unlock it by push/pulling the lock knob though. It's when I lock/unlock the car then this one lock fails to lock or unlock.
I removed the casing but couldn't see the whole lock assembly due to it hidden behind the corner of metal frame. But I did notice a wire plug hanging on its own, I believe this plug needs to be plugged in there but can't see where without removing the whole lock assembly.
My question is: does this plug definitely needs to be plugged in there somewhere or there's something else wrong with the lock.