The Sigs were suffering from failure to feed problems because of loose grips on the guns by the shooters. I have seen this many times when teaching semi-auto conversion classes to LEO's who had been trained on revolvers. It wasn't just with the Sigs, but other makes as well. However, the Smiths seemed to suffer from it less.

I traded my 645 for a 4566 to an FBI Agent who just had to have the gun Sonny Crockett carried in Miami Vice. I'm guessing that's where you 645's name came from?

P.S. The worst *** I ever saw on the line was a Beretta.