Hi, Blackhorse,
Cleaning will not resolve the problem unless you are very lucky. The cylinder stop spring needs to be strengthened and realigned, plus weight removed from the cylinder stop. Since you do not sound like an experienced gunsmith, I would second the advice to send it back to S&W.
BTW, you don't rap the sideplate with a piece of wood. To remove the sideplate screws you first have to remove the grips. Then relieve tension on the mainspring screw before removing the sideplate screws. Note the position of each screw as you remove it. With the grips off and the screws out, hold the gun, sideplate down, over a padded surface, and rap the grip on the top (opposite from the sideplate) with a piece of wood like a hammer handle. The sideplate will fall off.
After making repairs, make sure the hammer safety is back in place correctly, and then replace the sideplate carefully, making sure to engage the undercut at the top of the sideplate. Tap the sideplate lightly to partially seat it, then replace the screws, making sure each goes back where it came from. If anything interferes, STOP. Do not take a chance on warping the sideplate. After the screws are snugged down, screw the mainspring tension screw back in.
Jim