I thought I had this one fixed and covered, but nay, the central locking system is at it again.

I've been here before, but it's a bit different this time. Yep, I read all the other threads on this problem and this time it's a total mystery. So in hopes that someone has the same weirdness, I'm posting a new thread.

The symptoms are quite simple: the remote fob will unlock the doors, but won't lock them. The lights blink to acknowledge the signal, twice for unlock and once for lock, but the doors don't lock. That's it. I can use the key and the whole system works fine, but the fob will only unlock the doors when they're in the locked position.

I suspect somehow one of the doors is not sending the signal to the central system that it's in the unlocked position. That happened to me before when the rear actuator stopped working. In that case, the key fob wouldn't lock or unlock the doors because the rear door wasn't responding. I replaced the rear actuator last year, with an original but used part. It's functioning just fine this time, so I suspect the problem is elsewhere.

Any thoughts?

Rob