I'm having the same problem with my stock 3. It started on 7-25-15 and I wish I could tell you that I solved this... So far I went back (from a 10#) to the stock recoil spring, I added an extra power extractor spring and last week changed out my extractor... Yesterday on the next-to-last array it happen again, but luckily my R.O.
is a Tanfo shooter. After the stage he said "you need to get rid of that mag." He was telling me that the magazine is causing my problems, that the mouth of the mag is stretched. He told me to take a caliper to my mags... most of my mag's were .342" - .345", the mag in question was .362". The way I understood him (and I could be way off) is the bullet in the "bad" mag is sitting to high and when the slide is ejecting the spent casing, that bullet is hitting the bottom of the spent casing and when the slide is returning to battery is sending both forward....
I hope this works, because this is getting old...