I had a similar issues on my trailer.
I was testing everything, for our maiden voyage and noticed water leaking out from the curbside floor.
After digging into it I found the the fool that roto-zipped the hole in the outside wall for the electrical outlet had cut a nice U shaped hole in the kitchen sink drain line.
Water pouring out, while I was filling and draining the kitchen sinks, went into the furnace and ruined the control board.
I called my dealer and he overnight-ed me a new control board, paid for the parts to repair the pipe and sent me a check for the labor that Keystone would have paid for the work.
I always say that no 2 trailers, of the same model, are built the same.
-Brian