FOUND MY PROBLEM
It was the factory provided brake controller cable. Not exactly their fault though. The cable is just wrapped in a tape like shield. It was rubbing on something and wore through. The reverse wire was frayed bare as was the illumination wire. I guess (sometimes) when in reverse they shorted/touched taking out the fuse.
Little bit of repair and now the plastic wire wrap protection and I should be fine
Those of you with a brake controller may want to double check and see if it is rubbing before it drives you crazy too!
PS if anybody needs it I now have a spare dimmer switch
