having problems of this sort requires you to have some replacement boards on hand. you really can't trouble shoot this sort of problem. It can be caused by a bad cpu board, a bad power supply board, a bad input or out put board, or bad card rack. Also program boards can cause the shot gunning effect you have described. You can try unplugging the inputs one at a time and see if it stops. I would replace the cpu first. Adams carries most of these boards. Good Luck.