I had friends say they had problems with the same primers. Easiest way to check is to just try another brand of shells. It might be firing pins are slightly short, springs are slightly weak in the strikes they provide, the rim cuts on the chambers might be too deep and several other weird potential issues. Had a friend who shot Winchester AA shells in the lower barrel and Remington shells in the top. His was a firing pin issue and using the softer primer in the weaker strike fixed it for a couple years.
Did the smith check firing pin protrudion? Or did he just clean it, lube it and decide it was fixed?
