I just sent my one year-old 686 Plus back to the factory for "failure to carry up" on two cylinders. Two weeks later, I've got it back, with a new hand installed. S&W customer service is excellent. The OP should call the factory and send it back - unless he has access to a good S&W revolver smith nearby. (Caution: repairs reportedly slow down in August of each year as the factory closes for two weeks for vacations).
Revolvers are more reliable than pistols, but you still have to check on things regularly to detect problems and make minor adjustments -- especially if you shoot the particular revolver a lot. More so if you use hotter ammo (e.g., 125 grain .357 Magnum rounds). My extractor rod (they screw in backwards!) gets loose every now and then, and I've had the nut (it looks like it's a screw, but it's a nut!) on thumbpieces loosen up too. All that aside, my 686 has fired every time I've pressed the trigger, and its accurate, too!