I would try a different gunsmith.
I've found over the years when a "gunsmith" makes a comment like that it usually means he doesn't know how to fix the problem.
Most guns have little quirks, or certain problems that occur more often than others. Most knowledgeable gunsmiths are aware of these idiosyncracies and know how to repair them. I'm sure if you can locate a gunsmith worthy of the name he will figure out how to fix it.
Good luck.