So I bought a used 686-6 PC 7 shot. Very clean, everything functioned well. I wasn't thrilled with the Hogues and replaced them. Not a big fan of the nubby service hammer either. Obtained an appropriate target hammer from Midway, and sat down to swap them out. I expected, at minimum, to have to also swap the double action sears, but was pleasantly surprised to have a "drop in" exchange. Single action was clean, crisp, DA was smooth.
Then, while cocking the hammer very slowly to check timing, I found a weird situation: went slowly and the sear engaged. I kept pulling and it engaged again. Or seemed to. Like there are 2 sear ledges on the hammer, a MM apart, which of course there are not.
I compared it to the original and there are no obvious dimensional differences. I lightly stoned a few surfaces {not the sear) just to see if something would help. Nope, keep getting the 2 "clicks".
I am not worried about something dangerous occurring, there is no "push off" or any malfunction.
Anyone ever experienced this or even heard of it? Thoughts?

Just sent a link to your e-mail that may help you out.

I have the same Smith. Are you sure that you are not feeling the end of the cylinder rotation, then the sear? Mine feels like two audible clicks, first at cylinder rotation completion, then at the sear in double action mode. Once you get to the 2nd click its a light SA pull to let the hammer drop.