Sounds like you've got a short in the wall and/or keypad. Is the keypad wireless or wired? Also,was the cover to the keypad ever left opened when it rained? It's possible that the keypad circuit board got water in it, OR the wiring from the keypad and/or the wall switch got cut or snagged and is causing a short. You may want to try replacing the keypad first, then see if the door continues to open and close. If that's not it, then replace the wall switch, then try replacing the wiring to the main unit, in that order.