This issue still hasn't cleared up? Damn.. Anyways i had good luck with the Apex extractor on my Gen 3 17. I was getting BTF bad. I replaced the ejector and the extractor. I didn't have any luck. And Randy Lee at Apex was nice enough to fit it for me and test for free. Recently the little indexing tab broke off. I have no idea when As it didn't impede function. Then i started to get failure to feeds every 30 rounds or so. I think too much material has chipped away from the extractor for it to work perfect every time.
Anyways! Long story short. Your apex extractor may need fitted a little bit.