Just put some blue loctite on the threads of the coking rod, it'll keep it from moving, but then itll be kinda hard to adjust the velocity from the ivg so get it shooting at the right velocity before you loctite the cocking rod, and don't put a lot or it might be hard to get it back out
I'm a fan of using a turn or two of teflon tape on the threads of the rod, that usually works well too. If you go with blue loctite, let it cure fully before you screw it back into the hammer. If it cures, it'll act sorta like a lock nut does. Otherwise, you might have a bit of trouble getting the rod out again.
i had this same problem and i tried everything that was said. the only fix that worked was a new hammer. i even bought a cocking rod with a derlin post in it to prevent that from happening and it still would shoot out.
Could be. There's nothing "wrong" with either part, per se, they're just fitting more loosely than they could. Just has to do with how the threads were cut. I'd say try one of the fixes above (they're all equally good) and see if that helps.