Oh, and just to offer something I observed last night looking at mine (not to mention drumming up some traffic on this thread looking for somebody who has a shaft they will make me a deal on), I think I see why the dogs don't engage as well over time...
The ratchet mechanism is a ramp up, followed by a plateau flat section, then a stair step down. Each of the two gear pairs have this.
So going the "slip" direction, the ramps ride on the ramps up onto the plateau, and drop down the stair, and ride up the next ramp, and repeat.
Going the "catch" direction, you ride down the plateau, and then the "step" parts run smack into each other and lock. They can't "slide up" a step, just a ramp.
So on my worn pair, metal from the ramp had been carried up and gave the plateau a slight "lip" or "mound" at it's start. No big deal going forward, it's still a ramp.
But going backwards, where the "steps" have to catch each other, those complimentary "lips" kept the steps from fully meshing. So instead of having the full face of each step engage the full face of the opposing step, maybe the top 2/3rds of each step engaged. The gears would not seat into each other completely, and could not completely engage.
The solution was simple, take the shaft assembly apart, and put the face of each gear par on a flat surface with some sand paper, and sand off those little lips until they are flat again. It's obvious when you are done, the whole flat surface is shiny again.
I did this last night, and just by feel you can see that ratchet engages much more firmly and aggressively, even without the spring in place. So I think that will solve my engagement problem, after I solve my shaft problem.
For my screwed up threads on my shaft problem, I am thinking now about tapping a hole in the middle of that shaft for a retaining bolt with a washer and spacer... though if I can find a good deal I will just replace the shaft.