Not to get too far off the trail here, but just a reminder in terms of the many possible causes of misfires in DA..... "staging" the trigger in double action can cause what's called "hammer hits rebound". This "incomplete" rearward travel of the trigger in DA (staging) can result in the rebound seat on the hammer striking the hammer seat on the top of the rebound slide, causing the hammer to not go fully into battery, and cause misfires.
Just another thing to check for.....a little bit of "wink" (space) between those surfaces when the trigger is fully rearward and the hammer comes fully down.
Carter