Does anyone know what would cause this yellow light to flash rapidly while the machine is on? When the ball hopper is empty then it will turn red. When full the red goes away and only the flashing yellow light is left over. Machine has set for a year in a closet not being used. Possible dust in a optical sensor? I have reset the machine and still no change. Not sure what else to check as the machine works properly and pays out when you hit payout holes and jackpots. Any help would be appreciated. Pic attached.IMG_1516.jpg