USB GPIO board stops responding after high voltage relay with load is switched on
It seems that it's an EMC problem rising from the surge current of your load (a motor pump).
If you supply the relay board with the same 5v as the Numato board, it's possible to have some return spike on the 5v that hangs the Numato CPU when the pump start. Try to put some ceramic capacitors (one 10uF and one 100nF) next to the 5V connector of the relay board.