Jam Twice while installing about one square of rooging shingles the last nail turned upside down and jammed? They were very hard to remove. Suggestions?

I have noticed that some if not all brands are now using metal wire instead of copper to make coils. Metal wire is stiffer and does not bent down out of the path of the driver. If you are using coils welded together with metal wire (some wire looks copper collored, however when tested with magnet is found to be metal), and after firing a few nails, open side door and check if the leading wire is not bending down. Leading wire will not allow the nail the fully move into the path of the driver. Stiff wire will also cause the next nail in line to pull down slightly. When nail is pulled down slightly, it will be out of the path of the driver. The driver will hit the edge of the nail and cause it to flip. The nails can also flip if the feeder is not pushing the nails fully forward due to low pressure or weak spring or springs (some nailers have a spring pushing feed piston others use air). Finally, the feed piston or the body of the nailer where the feed piston is housed could be worn. With feed piston in forward position (normal) and the feeder claw removed, apply outword pressure to feeder with thumb checking for loose fit. The feeder shaft should not be loose nor move from side to side with thumb pressure. If shaft is loose then most likey lower body of gun worn with no repair. Good luck with you nailer.