Originally Posted by
mechBgon
If they're not connected, you may need a dedicated ground wire between them, or at least between the frame and fork. I assume your generator's ground screw is present and is penetrating the frame's paint to the metal.
I bet this is it. Weird thing is the taillight runs just fine on its own, and there's no ground screw in place. But perhaps the gen bracket is contacting some, ahem, iron oxide instead of paint where I can't see.