What it sounds like is a defective extractor or the extractor is in need of adjustment. Any gunsmith can do both, probably for a lot less than it cost to ship back. Since it's extracting about 90% of the time, my guess would be it needs adjustment to latch on more firmly to the casing. An easy way to test for this, is to field strip the gun. Take the bare slide and push a cartridge up from below into the extractor. The extractor should hold it firmly in place. If it's very loose or falls out, it needs adjustment.
Although this is a simple operation, your gun will have to wait it's turn. Depending on their workload, it could be a week or several months before you get it back from the factory.