Get rid of the red wire from the switch directly to the small board. On the stock boards, it goes to ground, so you're probably shorting positive to ground (through the jumper cable and TK-RX1x board) so the PCB traces burn up as the weakest component.

On the stock tank, that wire is only there to discharge things when the tank is turned off, but if you miswire it, you can damage things. It's not really necessary anyway.

D.