If the mixer in the coolingtray is stopping when there are a lot of beans in it you might need to adjust the resistance of the motor. Please find the motor that is driving the axle of the tray. There is a crown nut that you can adjust. Take the little key from the tool set, and turn the nut clockwise
Once the nut is tight lock it by bending a pin in the nut.
Now the tray should mix without problems even with a large batch of beans.