I had been given a few thousand .40 once-fired cases by a police sgt. friend when I discovered this phenomenon for the first time. What a shame. Most of the cases wouldn't size correctly without a roll-press (which I don't have).
I bet an overcharged .45 round would find the unsupported base and easy place to breach.
I have shot tens of thousands of rounds in Glock pistols. This has mostly been 9mm and 40. I also had a 21C that I liked very much. I was a police firearms instructor for a 300 officer department that used Glock and was a factory trained armorer. I supervised hundreds of thousands of rounds being put downrange so I have plenty of faith in Glock.
There are several plausible reasons for the malfunction here but the folks at the armorer school were very clear about not using reloaded ammunition in the pistol. Quality control is a serious issue with reloads and unless you do it yourself with great care I don’t recommend using reloaded ammunition in any modern semi-automatic firearm. Double charged rounds, squibs, primers not seated correctly, bullets that are too big, casings that are bulged, are the most common problems off the top of my head. Lead bullets or reloaded ammunition voided the factory warranty for a reason.
Glock is a terrific pistol no matter what you read or hear. Firearms are kind of like cars for enthusiast and everyone has their brand and a little suspicion towards others.
Pro Tip: You should always inspect your ammunition prior to using it looking for bulged cases, primers not seated correctly, malformed bullets, or anything else that does not seem right. I have seen flawed rounds from every major manufacturer but I have never seen a catastrophic malfunction with major brand ammunition.
Every firearm will wear out or break under heavy use but I still believe Glock is the most reliable firearm for the money.
Save your reloaded ammunition for large frame revolvers!