I got my 686 6" in January and the brass label shows it was shot 1-14-13 and I picked it up that the dealer on the 1-18 it is marked 686-6.Some of them might have gotten miss marked.
I just got a new 686 plus 6 inch a couple a weeks ago.Same thing as yours.Thinking about sending it in.It is sad that this kinda thing is acceptable when you know it just don't look right.
Hammer follow slide=the hammer is not catching the cocking peice (37) like it should for single action.Like said If it has the Smith & Wesson on the slide send it in to get it fixed.