Pivot shaft problems
Hmmm.
You may have run out of threads. There should be a large, heavy duty washer on that pivot. Like, a washer that's almost a 1/8" thick. So it you may have bottomed out the nut on the threads before you put enough clamp force on the pivot to keep it from spinning. Which is bad for several reasons, but you won't be able to torque that to spec because you won't be able to stop the pivot from spinning like that. Sorry I didn't see that before, I don't think the washer that's on there is original now that I'm looking at it more closely.
The other thing you can try is using a heavy duty lock washer as well. Not for it's locking capabilities, but because as soon as you start compressing the lock washer it will put a longitudinal force on the pivot pin. Basically it will start pulling on the pivot which will help to keep it from spinning. The other thing is that those lock nuts are really only intended to be tightened a couple of times. So you may need another lock nut, the threads may be trashed at this point.
The ones that come with the Firm Feel greaseable pivot shafts are just nylock nuts. Again, these get torqued to a very high number, which makes the locking action of the nut an extra safety feature. Torqued to spec should be more than enough to keep even a regular nut from backing off.
Here's a picture of the washer and nut that comes with the QA1 LCA's. The stock one's aren't this thick, but you get the idea.
Here's a shot of my car, you can see the nylock nut that's on there. But not the HD washer really. It's there, I promise.
And thank you guys for the kind words. I still learn stuff about these cars all the time, but suspension and setting cars up for handling has always been one of my interests all the way back to when I was 16 and started driving my '56 Austin Healey that had been prepped for vintage racing. I definitely don't know everything and suspension tuning is one of those things that even very experienced people have different opinions about.