Tamiya SRB ball diff will not get tight

[Saito2]

I've run into a strange problem with the second Tamiya SRB ball diff I've just purchased. I know the typical issues with it becoming loose and needing adjustment but my first one worked ok with stronger threadlock. This second one will not get tight. I assembled the diff per instructions, fully tightening it and then backing off 1/4 turn. It worked smoothly without slippage then. It sat on my workbench for a week due to time constraints before I got back to it today to re-install it. Now it slips badly. I've torn it down 3 times and reassembled it, but even with the screw fully tightened down, I can easily spin the diff gear while holding both outdrives. Are the disc springs bad? Did they lose tension and go flat? I'm really at a loss.

[Percymon]

I've not heard of disc springs going bad but always a first time.

Might ge worth examining them closely, perhaps you could shim behind them if the look good ?

[Saito2]

Yeah, I've never seen them go bad either. I'll try a shim. When I take it apart and examine them they still have their "dish". I kept rechecking to make sure I had the 2 big and 2 small disc springs oriented properly. Thanks.

[Saito2]

Ok, now things are getting weird. I'm not sure how or even if it went together properly the first time, but here's what I'm finding currently. I assembled the diff halves with rings, bearing and spring washers but omitted the diff gear and balls. I tightened the adjusting screw till it bottomed out (did not back off 1/4 at this point). At this point, I'm able to easily slip a diff ball between the diff rings. The assembly basically bottoms out before it puts tension on the diff balls. Next, I assembled it leaving out one of the small disc springs and was able to finally lock the diff by fully tightening it. Backing off a 1/4 turn gave back some diff action.

So my question is, what is causing the diff screw to bottom out before it puts tension on the balls when assembled as per instructions?