With a 20d nail and a little time at a bench grinder I crafted a replacement for the cutoff switch that seems to have returned the butter smooth feed. Even after doing this I gotta admit I don't really understand how the cutoff works. I was concerned that it would be a problem that the nail is about .015 smaller in diameter but in fact that made it a lot easier to reposition it in a trial and error process to get it right. The little clamp on the sight seems to have it secured in place.

Btw, a repacement cutoff switch at Numrich runs around $35!