[Wiscbldr]

Check that there isnt anything in the way obstructing it, that its not a windy day and its shifting the garage door, and also check to see if there is direct sunlight going into one of the optical sensors as that could affect the lasers. I had that happen one day, and would only happen during certain hours, times of the year when the sun hit it just right. You can also check the sensitivity levels for going up and down as they might be off. You could also disconnect the cord and freely roll it up and down by hand to see if its hanging up anywhere.