I'm back from the range. The first 59rds ran perfect with very good extraction using three magazines. At round 60, the first failure to extract occurred (same type of failure as before). One of the magazines had 3 failures to extract, and the other two had one each. I fired 100rds, and I load 10rds in each mag for reference.
Another disappointing day, and I'm not sure how to proceed. The spare Wolff extra power CZ spring I have is about .012 wider than the stock extractor spring and is not cone shaped. Should I ream/grind out the angled extractor spring hole in the slide to accommodate the CZ extra power Wolff spring, or should I move on and sell this C100 with disclosures? I would do the reaming with a Dremel. It's been a fine, tight fitted handgun, and I always said I would never sell it. I ran today with the new recoil spring and extractor spring, both recent factory replacements. The extractor claw looks fine.
I'm all ears right now, and I hope the members with much more experience than I can come up with a good suggestion. This is a $350 handgun that's just over 5 years old with about 4000 rounds fired.
One last note, I did put an unfired round under the extractor claw when I changed out the extractor spring to see how well it was gripping the round. I shook the slide pretty vigorously and it held the round without a problem.