It may be as simple as this...
I am assuming that -like me - you keep your rifle clean and lubricated as appropriate. But maybe - like me - you do not have one of those bolt take-down tools. Having gained the impression that dismantling the carbine bolt was well-nigh impossible without one, the carbine was - up to now - the only one of my rifles which had not had the bolt assembly dismantled, cleaned and re-assembled.
Big mistake!
Training for an imminent competition, my (previously) flawlessly functioning carbine started to mess up the ejection. First one "half-stovepipe", then every now and again, then every single time. The cartridge ended up half out of the chamber, with the next round jammed in underneath. I had to finish the training session by loading rounds individually - very, very tedious!
At first, I thought that the extractor was badly worn, so that the rims were slipping out of engagement with the extractor as the case started to come out of the chamber. But examination under a watchmaker's eyeglass showed that this was not the case. The extractor looked fine - the trouble was simply that the extractor could not move in close enough to the bolt body to hold the rim reliably. I suspected a "foreign body" in the gap.
So I dismantled the bolt without a takedown tool. For those who have not done this, I can assure you that it is an exercise to be avoided. Nevertheless, I managed it, and discovered that the cause was not a foreign body, but quite simply hard-packed residues that required a brass brush to remove them.
For those who have not tried to re-assemble a carbine bolt without the takedown tool, I am now able to confirm that this is an exercise that is even worse than dismantling, and requires three hands with steel fingers. In the end, I had to make an impromptu jig to hold down the ejector stud while finagling the rest.
But having re-assembled it all, the extractor closed up properly, and is now fully functional.
Lesson 1) In accordance with Murphy's Law, you may have got your machinery 99% cleaned and oiled. It is the 1% you missed out that will cause you pain.
Lesson 2) If you are an active shooter, get yourself a bolt takedown tool a.s.a.p.
:wave:
Patrick