This also happened with my Long extractor 2014 production P229R. In 3000 rounds, the exact same failure occurred 26 times with various 10-round magazines and different factory ammo. Nothing helped - I installed a new extractor/spring, and even bought a complete replacement slide but the malfunctions still happened. The Sig CS rep also gave me the "that's not that many" spiel. I sent the original gun and slide back to Sig, and got it back in less than a week. The gunsmith comment stated that they "updated extractor spring" and "test fired with 30 rounds Winchester 115 grain with no malfunctions". By that point I had given up, sold it, got a Glock and never looked back.
The above noted failures.