Same problem with an STI before, if you dont have any gunsmithing experience send it to a good gunsmith. I had mine worked my Ortiz Custom Guns in Savannah, GA and the problem is gone, the issue was extractor, it just needed to be fitted. The edges were really sharp so he rounded them a little bit and changed the angle ever so slightly. Again send it to a reputable gunsmith, Pedro over in Savannah charged me $45 to 50 bucks if I am not mistaken and the gun is flawless.