Quoted from G-P-E:It appears pin 3 (voltage tolerance) pin was left floating on their design.
That input is supposed to be tied high (reset at 4.5V or 10% VCC tolerance) or tied low (reset at 4.75V or 5% VCC tolerance) and should never be left floating.
Adding the jumper from pins 3 to 4 selects the 5% tolerance. If the 5V line dips below 4.75V then your board will reset (which is what it is supposed to do with that setting).
Great explanation. It seems years later Rottendog is still not as reliable as they claim to be.