I've did some tests to see if I'm be able to create your fault on the motherboard but without success. I have measured some vdc voltages on the board, it's random but maybe you find some faulty voltage on it which may give a direction were to look further. When you measure the sensitive crystal side, the box may crashes, the display goes off, two blue leds flashes, or goes on or off. When measure this spot you need afterwards to switch off the box, and turn it on when it's unloaded. See picture, click on it for a full view.