I haven't tried it on a 2340, so you may have found one of the other 5% of the guns.
I had the same problem with one gun, but found that I simply didn't crank down on the slide tightly enough. (That's why they give you an allen wrench; tighten all of the bolts, not just the main one.)
(On another one, I neglected to back out the set screw. I really felt dumb...)