I'm with Roger. There could be any number of issues earlier on this can cause problems. I'm not a believer in the use drills or other things that intend to manipulate the release point. This action is happening so fast that you won't really be able to do much about it in a direct way. Solid, repeatable mechanics that are practiced in an environment as close as possible to what he will be facing in games is key. For example, target practice on flat ground, at less than game intensity and/or from the wrong distance, will not translate to the game environment and may even make things worse.