Thanks for the response! I read through some threads about lock removal, but thought I understood the symptoms to be different for those cases - it sounded like their problem was the key did nothing when turned. In this case, the key is apparently engaging within the lock, and obviously hitting something, since the lock knob moves. It's as if it isn't quite connected, and since this appeared suddenly when the lock knob post was left disconnected, I was hoping there was some other connection I'd overlooked when I re-hooked the end of the post into the two obvious holes while the door panel was off. Hoping for a photo of that assembly, a drawing.... a schematic...

One thing I did wonder about while I was in there - the two metal tangs, or levers had holes for the post to hook into, but there was some wiggle room in the door, and it was unclear which of those two pieces was supposed to be on the outside. I tried them both ways, and then picked the way that felt snug. Is there a way to tell which way they go, or does it matter?

Looks like I'll start by taking the lock out, next free time I've got when the sun's shining. This time I'll grab the camera!