There have been some rolling changes to the guns, I'm not sure what exactly has been done, and the current mags are marked "03". The guns currently being produced, along with the "03" mags that have the latest follower design, to seem to be reliable. I believe the 42 as well as the 43/43X and maybe even the 48 may be a bit more dependent on a decent grip to function properly than the larger Glocks.