Glock had a bad batch of G22 pistols (E series) get released a few years ago. The frame rails were pretty weak in this batch. You never knew there was a problem until the gun was field stripped. At that time the rails would sometimes fall out!
Sounds scary but think about it.... The gun was running all the way up until the time you took it apart. At that time it was evident the gun was broke but...... It was still running until that time.
Pretty cool indeed!