Saw this at automags as well but I'll answer it here.
One possible area you might want to explore regarding this is the barrel locking mechanism.
Now different barrels have different outer diameters and have the locking grooves milled in differently, you can adjust the spring tension in the locking stub by an allen key. It should be in front of and above the trigger, wind the screw in = more tension. (you might have to take grip frame off, can't remember off hand)
Now this will lock the barrels in to different degrees, the problem might have been barrel wobble? by locking them in tighter this can be prevented if not excluded entirely. The bolt might have caught on the lip of the barrel maybe?
Hope this helps, e mail
bad.dave666@btinternet.com if I can help.