I have PW and PL on my 87 Westy.  Every year or two one of them goes nuts.
The hardest one to troubleshoot is the locks.  In my case, every single time
is was broken wiring in the door-body hinge area.  Usually the drivers side
because it gets more fatigue.  I would check that first.

John
87 Westy SVX

PS My power locks just went into full lockdown mode a couple of days ago.  I
haven't started trying to fix it yet but the wires will be my first place to
look.