FX New gun discharges air in my face on 7th shot

That a very light slug. Chances are slim that the projectile got stuck, but not impossible.
I doubt it, they are very consistent on their sizing, from my inspections .0001", if one goes through they all will. And before you ask, yes I can measure down to half of that accurately, did for 35 years. The FX hybrids are made by RMR.
 
Puff of air, won't fill....
It sounds like it may be the small O-Ring on the screw that seals the drilled hole for factory access inside the block. You know, the small screw at the rear of the top of the grip.
Maybe?

mike