As a Glock 21 owner myself, I've heard of the Glock Ka-Boom stories as well.
I seem to recall that they were guns in use by the Portland Police Department. For what it is worth, Glock seemed to have problems with the investigation results from the Portland PD.
Also, I've read that they were Gen 2 models, with less chamber support than current Glock 21s.
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Ladyfriend: "I need help with the leaves in the yard"
Me: "Controlled burn?"
LadyFriend: "I forgot my Boy Scout turned into an infantry officer."