Most common was light strikes. The kit that ISSC sends out for free fixes the potential issue. Mainly had to do with the screws holding the action in place coming loose I believe, I havent had that issue myself. The first versions also had too short of screw in one area, that has since been replaced with a longer one as well as a washer. There are a couple good threads on here about fixes for the first version. The newest ones all have the fixes out of the box. Not sure if the latest come with the kit preinstalled but its for free from ISSC and they pay for shipping as well. Its a great rifle, just got a bad rap because of the issues it had when it was first released.