Once you've got the false set, back up a little bit until the pins are just about to fall back into place. Then, re-lift each one in turn, and then it should be possible to get each pin to true set at the shear line. I've always had more luck overlifting security pins and letting them set on the way down, than the usual method of picking up until they set.
Security pins are tricky things... I had reasonable luck by trying a lock with a single security pin in it. The lock went to false set, and so I felt around to figure out which one was the security pin. On my first pass, I wound up kinda brute forcing the bottom pin into place, but with more practice, the finesse started to come into play. I'm going to go back and add more security pins to it to get the feel down.
