A while back I had an intersting dead short issue. Not saying this is the same as yours, but perhaps as easy. I had some stray staples left over from when the trailer was made that had found their way across the positive and negative terminals on the back of a 12V light. The light worked fine one day, we traveled to another destination and then the fridge wouldn't turn on. Yup, same circuit as the light that was shorted out.
Tow Vehicle: '92 F350, Crew Cab, 4X4, Cummins 5.9 24 Valve, 6spd.Driver:Clint, Navigator:Melanie, Entertainment: 3 Boys (24,22,20) and now girlfriends too, 1 dog (Great Pyrenees/Akbash cross). Mission Statement: Just another adventure! Towed vehicle:2009 Roo 19 with lots of mods!