Stanley Bostitch N88rh Framing Nailer Driver Piston 158582 "nail gun popping" Questions

gun is set at 120lbs. May occur when headvalve or driver is stuck (will usually make a pop or click when tigger is depressed), or tigger valve has failed or safety not actually touching trigger firing

I have a Bostitch Framing Nailer that I bought used. No manual. I used it once, and I noticed that it fires two nails (POP-POP). I'm only looking to shoot one at a time and it shoots two. Is there ...

nail) and other times it shoots two nails at once. Also when it shoots two at once, it usually doesnt need a trigger pull, just need to compress the nose. Worn trigger and or worn firing valve. Remove