I sure hope you plan on telling the next owner about your experience with this rifle.
And, one gunsmith, who may or may not have been familiar with the rifle, wouldn't ease my conscience if the next owner got hurt because the problem re-occurred.
I know its a bite in the butt, but, I don't think my conscience could rest very easily after I sold the rifle for anything other than a wall hanger, making dang sure it was disabled from every firing another round again.
And, frankly, I am surprised the Gander Mt. Gunsmith gave you a go ahead to re use the rifle, did you get it in writing? Cause if somebody gets sued, you better have either a no fire letter signed by the buyer, or paperwork covering your butt.
I myself, would torch the dang thing, eat the lost money, and sleep better at night.