Thanks, Eric & Chris. I did chat with Reef Photo yesterday and they know of the problem. I overnighted my housing to them. Their feedback was that the tolerances in the Nikon switch design are broad enough that the standard switch mechanism can't function across all bodies. Whether that's true or not, they have a fix, but it is a fix for my specific camera body, which I don't like. Either way, yes Eric, my go-to will be back button focus and the switch will become my back up.
Thanks for all the help.