There's two problems with this: First, a round could not sit in that position because the ejector (a small piece of metal that sticks out of the breech face when the slide is in the rearmost position) would prevent the extractor from engaging the rim of the cartridge, as it is designed to do (although this is possible with the Glock [by inserting the round from the top and slipping the rim into the extractor, having it sit on top of the ejector], it would require manually inserting the round into this position, and even then, would be misaligned with the chamber opening). Second, the slide is not moving far forward enough in this distance to strip a round from the magazine. If it was, it would not be possible to load a gun by inserting a magazine, and then hitting the slide release, because the slide would not be able to push the cartridge out of the feed lips by pushing the back of casing's rim.
A simple fix to this would be ensuring all rounds remain in the magazine when the aforementioned action is performed.
EDIT: After looking through the forums some more, I've realized the first problem is basically just an extension of an already-known issue. I'll leave it for anyone who cares to read it.
The second issue is Glock-only: the trigger disconnect apparently doesn't function when the slide is released forward from being locked in the rearward position. To see this yourself: completely unload the weapon (no mag, empty chamber), set the fire selector to semi-auto (V, tab sticking out the left side) and lock the slide back. Next, insert a loaded magazine. Now, while holding the trigger, release the slide (by either pulling it back and letting it go [R], or hitting the slide stop lever [T]). The weapon will fire one round.
The problem: in a real Glock, the trigger disconnect ensures that the weapon will not fire more than one round per pull of the trigger. Since in this state the weapon would essentially be halfway through its firing cycle (AFTER the trigger is pulled and the round in the chamber fired), the disconnect would be in effect, preventing it from going off until the trigger is released and pulled again (note that in this state, the trigger should be forward, held there under the influence of the trigger safety [that little tab of plastic that sticks out the front of Glock triggers], although when pulled, it should stay depressed).
The fix: when the above is performed, the weapon should NOT fire when in semi-automatic mode.
ANOTHER EDIT: My game must have been inconsistent at the time of testing.
Thanks for your patience in taking the time to read this