Door lock question

[dave`12]

1967 c10. The door will not lock when closed, it will lock when open, but unlocks when you close it. Something is hitting that keeps it from toggling when closed.

The (I'll call it a latch assembly) that is on the door that goes into the latch of the cab wiggles a little. The screws are very tight, and the wiggle seems to be unrelated to the tightness of the "latch assembly". From what I can reach from the jamb of the open door (door itself, not the cab). I don't see any adjustment in the "latch assembly" (at least from the outside) or the latch attached to the cab.

I took off the door panel, but it is just about impossible to see what might be the problem.

any ideas of how I can fix this?

thanx in advance

dave