maybe your extractor spring is too stiff?
I had a 7.62x39 AR that was running fine, but decided to upgrade the extractor spring to the "Colt Copper" spring, because the internet said so. This is when 7.62x39 was cheap, "before the war", when 1,000rd cases of Wolf were $230, IIRC.
The very next range outing, my first mag, the extractor broke, the only time I've ever had an extractor break. Granted, the 7.62x39 AR is one of those cases where the rim of the bolt is already marginal, but it was working fine before that. Perfect case of "cause and effect", might as well have been a flashing neon sign.
Anyways, I went and got a new extractor, "machined" billet steel. and went back to the original extractor spring, was fine after that. And, I've never had a 7.62x39 bolt break either, I guess modern metallurgy has come a long way.
I guess there's a lesson in there somewhere.