This sounds like what happened to me. The problem was a broken wire in the
bundle passing from the drivers door to under the dash. If you look at the
wiring diagram you would see that a broken wire in the circuit acts as if
the lock on the other door was activated. A traveler wire of sorts like a 3
way light switch. On my westy many wires were just barely long enough when
installed. I spliced in an extension in both doors since opening the doors
pulled the wire bundle tight. A good look at the circuit diagram(bently
manual) helped me to understand it. Replacing the actuator doesn't fix a
broken wire. You can spend time (or money for someone else) to replace the
actuator or do a continuity check first on the circuit wiring. If a new
actuator doesn't fix the problem then  you have a wire problem. Do both door
locks cycle?

Bob
88 Westy