opener doesnt stay closed or go down on it own.

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Craftsman unit wont stay down and you have to hold the button to make it keep going down and once it hits the bottom of travel, if you dont let off the button just right, the door goes back up and the lights flash on it. It appears the safety devices at the bottom of the garage door are lit up. There is a outside access panel, car remote and inside control at the service door. I am not sure why this unit wont go down and stay there. You have too hold the button inside to get it too go down. it will open with car remote but wont close. It will open and close with the outside access remote. Thank you for the help. em-igottasellit@aol.com