On the opener itself there should be an adjustments that allow you determine the amount of force the garage door opener will exert when engaged in the closing procedure. This makes your garage door go back up in the case that you didn't pull the car in enough or your neighbor kid left his bike under the garage door. Try adjusting the down force 'up' (so it will exert more force) a bit. Makesure that you have no part of the garage door that is rubbing or grinding on something and that the drive chain/screw has a lube on it. Also check to make sure that the lift springs aren't jameed or wrapped up in anything or that one of the springs hasn't slipped. If the lift springs look like one is twisted wheras the other isn't (by matching up the paint marks)call a garage door person to check it out, those lift springs have a of potential energy waiting to ring the fingers from your hands.