[FlyFish]

Two thoughts -

You should be able to tell if the shellplate is advancing sufficiently by attempting to move it by hand after advancing it with the press handle. If the pawl isn't rotating it enough, you'll feel it click into place.

I had a somewhat similar jamming problem with my LnL press that involved the decapping process. When depriming, the spent primers were getting stuck on the depriming pin, and then partially reseating themselves on the upstroke, which would prevent the press from advancing. Often, the first jam would result in the primer dropping off and then I was able to continue normally. It was a problem with some die sets but not others. I eventually fixed it by doing a little polishing on the primer punches for those dies that had the problem.

I wouldn't think that either of those things would lead to the primer cam wire breaking away.