So today I removed the rear seat cushion, and the seat back bolster on the passenger side. After removing the window shade and all appropriate trim and screws I was able to remove the door panel.
This was made easier by a couple things. Two years ago, a local shop installed a new window regulator for me. Apparently, after breaking many of the push pin fasteners, they did not bother to replace them. Additional, the main sunshade, and the plastic panel next to it had come unglued from the door panel. I will re-glue these in place, and have new pins for re-assembly. The shop also ripped the damn interior foam door panel. This is a specialist German shop. Everyone is a bit of a hack, apparently. To be fair, I should include myself here. I broke the lock tab on the interior door handle cable, so I will need to find one of these.
Anyway, gaining access to the door lock actuator, everything appeared to be in order. cables and linkages all looked fine, but my moving the various levers did not open the door. I continued to move the lock up and down, cycling the levers, no response. Last, I grabbed the actuator as best I could and tried putting pressure on it, maybe a twisting motion would be a good description- and then I felt/heard something change and moving the levers now opened the door! Success!
So now I will remove the actuator and turn to those threads, not sure if I need to replace the actuator or if there is some lube or repair that will effect a cure. I also need to source a new cable, and glue the bits bck into the door panel, but boy am I glad it is now open!