I have a Remington 12-A 22 pump that the cartridge retainer broke. I took it to my local gun smith and had the retainer replaced. I didn't take the rifle out the case to shoot for 4 years and when I pump the a cartridge in to the chamber and the new cartridge retainer jams and falls out. How do I assemble the cartridge retainer? Any idea's on why the retainer would break?