I have seen Glocks let go. 1911s, Beretta M9s, M240s, M249s Colt/FN M4s, etc all of them have failures (usually ammo related (or in the case of GPMGs and LMGs firing too much ammo too quickly and overheating the weapons, which os more of an operator issue than a weapon failure as far as I am concerned) and let go at one point in time or another.
I have also seen PLENTY of AK-47s fail in spite of what the general public believes through tall tales about their reliability.
It can and does happen. Anything that is a mechanical device is subject to failure. While it is my opinion based on observation and experience that the Glocks primarily the full size Gen 3 9mm such as the G19/G17) are about the single most reliable semi auto service sidearm available, I don't think they are impervious to failure.
Even Ruger Blackhawk revolvers can and will fail from time to time. It happens.
