/ NH TC45 Flashers- this is weird.... #11
I just found this thread, and I see I am late to the show as you have already fixed it. I was going to suggest to follow the wires to a connector plug. Most likely the ground and hot wires are inserted into the wrong cavities in the plastic plug half. I am not familiar with NH wiring, but you can usually remove the wire from the cavity by releasing the terminal with an ice pick. Then you can reinsert into the correct cavity. I know this is too late for you since you have already cut and swapped your wires, but maybe someone else who has a similar electrical gremlin can benefit.