What you're saying is that you had an FTE...Failure to Extract...where the empty case has not extracted and is still in the chamber with the next round nosed up under it ?!
This can sometimes be caused by limp wristing the firearm...where the gun was not held firmly enough to allow the recoil of the slide do its job and extract the fired case and allow the next round to be chambered.
I've had two fail to loads on my new Gen4, both were user error. First one I had my thumb in the wrong spot and the slide bounced off of it. The second one a friend of mine had never shot before so she limp wristed it. I'm using the cheap federal ammo for range fire and it still loads great. Call Glock and they can help, their phone service is fast as hell.