I bought a P9 when they first came out and it had extraction issues. I communicated with Kahr and the gunsmith, Larry Meyer, informed me that extractor tunnel hardware might the cause by putting incorrect tension on the extractor. He suggested returning the gun, but I explained I had owned an MK9 and was familiar with working on Kahrs and thought I could fix it myself with the replacement parts and did not want to be without the gun for the estimated turnaround time. He kindly sent me all of the parts involved, including a new polished extractor, plus a replacement recoil spring. Replacing the parts instantly solved the extraction problems. Extractor tension can be a source of problems, as it apparently was in my case some 15 years ago.
There can be other possible causes for problems, of course. Someone told me he never made the same mistake twice, as he quickly went on to bigger and better mistakes. Maybe that is the case here.