My Legacy 696 CD / B Garage Door opener just stopped working. The door motor humms for about 3 seconds and then shuts off and the door did not move. I unhooked the door and then reattached it to the opener in the up position. At which time the motor engaged and the door moved about a foot and then it shut off again. I have checked and see no obstructions blocking the door from opening or closing. Safety sensor are still Green and Red on the LED indicator lights.