Could be the scears. Did the mechanics stone the scears? What about the Safety? Is it automatic? Can you take it out of service & try?
The problem first occurred prior to anyone opening up the rifle.
The gunsmith checked the safety, it the wood maybe had caused it, the triggers and sears but found no evidence of anything wrong.
He adjusted the pulls to a crisp 4 and 6 pounds.
Firing the gun again everything was great until a dozen total right and left barrel shots.
Then, "presto", a 12 lb pull was once again required for the rear trigger.
Back to the smith for another inspection. After nearly an hour he found nothing.
Pulls were 4 and 6 once again for less than a dozen shots...
Now, I am seeking information from all...