One possibility is that the stop could be bent. If you look at the schematic for a 32 Safety below, you will see a stop that part number 450 and it is very long and thin. The 32 and 38 Safety revolvers had similar stops in all models. I assume that your gunsmith did not disassemble the gun? When the spring pushes the stop up into the channel, it rests on the underside of the frame. If the thin arm is bent down, the stop will not rise to the proper level.
The stop moves so easily that even a weak spring should still push the stop up in place. If you push down on the stop, does it rebound or remain in place? Also, if you remove the stocks, you can see the stop spring (#454) pinned to the front of the butt-frame. You can see the spring and the back of the stop move if you push down on the stop. If the spring rebounds, the stop is bent. You can also take a small screwdriver and lightly lift the spring to see if it moves without taking any parts out. At rest, the stop should be about .060" high in the channel. Check these issues out and give us a reply.
Lastly, maybe Tom can clarify what actually moves the stop? Is it trigger or hammer actuated?
