I’ve seen posts about this problem online, but no one has listed a good fix. There seem to be LOTS of '06 Lucernes with back doors that won’t open. It is not a child door lock issue as the customer has no kids needing such protection, and the door should open from the outside anyway.
I need to remove the inner door panel, but can’t figure out how to do that with the door closed. Once the door panel is off, I can probably see what’s going on inside, and maybe fix it.