I called AA and asked about this issue, the way around is it to backup that brass nut gradually and test the shifting until it shifts ok then measure the distance from the brass nut cap to the top of the fork then...........grind the brass nut with same amount to shorten it.
According AA instructions, the brass nut is to take the guess work out of using the original screw but with this brass nut, it's just the same but with even more work and if you grind too much off that brass nut you're screwed
I haven't worked on my truck in couple weeks due to illness but will have to resolve this.
Try to find a washer, or spacer to go between the brass end cap, & the shift fork to space the brass cap out, & relieve the spring tension, this way no grinding on the brass end cap. Try different thickness spacers, until it shifts.