I have a RepRapDiscount Smart Controller. How can i calibrate the encoder? The encoder scrolls like crazy through the menus. Sometimes one click scrolls down one items, sometimes three. Also, sometimes when i rotate it down, it scrolls 1-2 items up then it scrolls down. Or when i rotate it up, it scrolls 1-2 items down then it scrolls up. So it is not because of encoder direction. how to solve it?