The original use of an inertia block was to prevent this. A clean and undamaged sear and hammer notch are also important. I suspect that the Gun Dr. could look at the hammers and sear and fix the problem quickly.
If it were my gun, I would try two or three different things and see if they worked. If they didn't, I would then send it to Gun Dr. He could fix the original problem and the other things I messed up trying to fix the first problem.
Pat Ireland