Given the mechanics of the Smith guns, i woild think the issue being the point that the sears are engaging the hammers. The sears should be longer or the hammer notch farther back. Which will allow the hammers to cock later.
OR the hooks on the cocking cams or cocking spurs on the hammers could be worked down to make the hammer not move back as far when cocking. That is the cause of the issue... the hammers are being caught by the sears too soon and they are being pushed back farther past that point when opening, and then mainspring pressure is wanting to close the gun back up some until the sears stop movement.
If the gun is unmolested, it likely was just not set properly when made.
