There are any number of reasons why adjacent chambers will not shoot to the same point of aim, and it's usually (though certainly not always) a manufacturing defect.
Problems from the factory can include chamber throats that are over- or under-sized, having the chamber bored at a slightly incorrect location (either relative to other chambers or to the cylinder's axis), a rough throat, or the chamber being bored at a slight angle. In some of these cases, careful experimentation with freeplay at full lock will occasionally improve the situation.
Other causes that can be either a defect or wear include lockup that is either too tight or too loose, a worn cylinder bolt resulting in chamber/bore misalignment, excessive wear on the cylinder yoke resulting in excessive runout thus causing misalignment - well, you get the picture: it could be ANYTHING. Without a proper checkout with the gun in hand, it's hard to know for sure.
In any case, I'd send it in to S&W with test targets. It is most likely a defect, in which case they're generally quite happy to fix it for free.
Do keep us posted.
