I believe something similar happens to the gentleman in this video. His theory is the round fired is weak, strong enough to eject the spent casing but not strong enough to get the slide back to pull a cartridge from the magazine. I have not had that issue with my SR22.
http://www.youtube.com/watch?v=FWNRG7xBPPk
****Sorry, someone had already posted this video earlier in the thread and I overlooked it****