Something else I just thought of, what kind of brass are you using? If you are using different kinds of range brass, I have noticed a big difference in case length when it comes to 9mm brass. If your cases are different lengths, this will change your crimp, and could be a factor in why some cartridges fail. I use range brass, but have had my best results when I sort by headstamp. I also measure a new batch of brass after sizing. I don’t trim them all to the same length because that is too much work for cheap and easy 9mm brass. What I do is discard any that are too short or too long. Hope this helps!