If the trouble is the same as I've seen, the second suggestion you (Dave) make could be the fix.

What has happened in my experience is the central lock actuator's rubber bellows water seal rips and allows water to follow the linkage down into the actuator's motor, binding it up with iron oxide. I'd say "rust," but those in Florida might not know this term.

I just forced the lock to move by working the lock button from the inside, but it is conceivable that oil dripped down alongside that linkage would, like the water, find its way into that rusted motor. Might need a lot of it and it might make a mess, but it does sound like it might help.

Many of the actuators I have pulled show this same failure of the water seal.



--
Art Benstein near Baltimore

"Being nice to people is so much easier with your mouth closed." -- Benjamin Davis