edit: This was all incorrect and a factory reset on 2.15 jogged another switch into working!
For visibility, because I do not know which thread is more appropriate:
I had an interesting side effect to flashing with the harness. I posted about it over in the enhancements/bugs thread, but will link to that here for visibility.
Short explanation: Light switches have never acted as routers (repeaters). Had to use the harness to update one out of seven switches. That switch now works as a router, with devices connecting through it, while the others do not.