I've had the same problem with my 9mm 229. It looks like below. Anyway, I had a local gunsmith look at it and declare that the extractor was in spec and there were no flaws. It still didn't work. It was then sent to SIG who replaced the extractor. It worked well for about 100 rounds and then started doing it again. It did it with more than one brand of ammo and with different magazines.
Since discovering that the problem still remains, I have not shot it again. I'm kind of ****** about it. It's the most expensive handgun that I own and it's the only one that has had a problem, so far.
I have had mine for about four years and I bought it used but in excellent condition.