The only problem I've experienced with Glocks is that they tend to multiply .
G20, G22, G29. Never experienced any problems except 1 failure-to-extract a Blazer 10mm case. The case rim (aluminum) was torn/gouged so I atribute it to ammo failure, not gun failure.
I've got over 10,000 rounds through my mod. 22 and the only problem I've had is a broken slide stop,(which I replaced,also bought a spare) and acouple of ftf.
The following URL will take you to one of the few Glock breakages I've heard of, or had close experience. Mr. sprey is my business partner. You will also notice that he meticulously documents everything about all his guns.