Took a while to figure-out, but it was really simple...

What was interesting was that when the door panel was off, the lock worked, but with the panel on, it didn't.

I finally realized that with the chrome bezel in-place, it held the interior door handle out a bit. This put just a bit of tension on the latch linkage, preventing the lock from engaging.

Turns out that when I re-assembled the door and installed the lock and handle mechanisms, I put the inside door latch too far forward. Moving it back about 3/16" inch resolved the problem. Not only that, the inside door handle is positioned a little better than before!

One less item on the Datsun "to-do" list.

There ya go Julio. Sometimes taking stuff apart, then reassembling it cures the problem. The horn on my Z has never worked since I got it 3 years ago. I had to replace the light switch. When I reassembled everything, I noticed the turn signal - to - headlight bracket was not pulled up correctly. Moved it, tightened it, and the horn started to work.

Don't you just love it when the gods smile on you and the easy fix works?

Shhhhhh...it happens.