Central locking acting funny

[TerminatorX5]

Hello.

Recently I had a problem with the rear left lock:

when I drive off, the doors normally lock. Now, only 3 of them lock and one is not locking.

When I use the console button to lock the doors, 3 doors lock and 1 does not.

When I use key to lock the doors, all 4 lock.

When I use key to unlock the doors, only 3 unlock.

If the rear door is locked, and I try to unlock using a button, it does not unlock.

So, this pattern indicates that the door will lock with the double locking but will not respond to any other lock/unlock commands.

Is this something with the lock hardware, cabling/pins/bolts?
Or is it something electrical, like blown fuse or a relay?
Or the "lock brain" has gone south?

Any ideas?

Thank you,