If you garage door is lowering then reversing back to the open position there could be something obstructing the sensors.
Garage door opener why the door slide back down.
Garage door opener problem.
We recommend unplugging the garage door opener and then replugging it back in after any repairs or adjustments to reset the system.
Door sliding back down once the door is up all the way it s resting on the horizontal parts of the track and the resistance of the motor to turning because it is low geared should prevent it coming back down.
You will have to take the cover off the motor unit to check the gear.
It can also be caused by dirt on the sensor eyes loose or corroded wire connections at the sensors or the motor head or just that the sensors have gone bad and need to be replaced.
Slipping down a few inches after opening posted by nashbamafan on 5 10 16 at 12 35 pm to sicboy probably have 2 springs above door and one of them is broken.
The one that is not is not strong enough to hold door up on its own but strong enough to still open the door.
It will be obvious if it is going bad.