With the subcompact Glocks there's more of a chance to not lock your wrist since there's less grip to get a hold of. It's common for the sub-compacts to through rounds back at you if you're not aggressive with your grip. Try being aggressive with a firm grip and locked wrist next time you're at the range. If that doesn't fix your problem, we may need to look at which ejector and extractor you have in your pistol.