Picked up my pf9 yesterday. It is slightly used. I know I have read several issues with extraction. I was only able to fire about 20 rounds of PMC through it and about half of those failed to extract. I polished the chamber and did a general F&B on the gun. I'm gonna try again when I get another chance and with different Ammos. It's a SN S1G**. Does this seem like a serious problem to anyone or should I just keep shooting to see if it breaks in any?