I saw this happen on a G-21 with an old style extractor that had a chip out of the very bottom of the claw. It was easy to miss in an inspection. It must have been a problem, since Glock came up with an upgraded 5-degree beveled extractor on the .45 and .40 cal guns. I'm sure that it could happen to a new style one too.
P.S. Is the extractor spring and plunger installed correctly?
Blessed are the peacemakers: for they shall be called the children of God. Matthew 5:9