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.
Garage door opener why the door slide back down.
Thank you for your question as to why the garage door will open all the way but slides back 6 inches.
Check to be sure these two sensors on either side of your garage door.
The one that is not is not strong enough to hold door up on its own but strong enough to still open the door.
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.
You need to check the door springs and the drive gear in the opener.
We recommend unplugging the garage door opener and then replugging it back in after any repairs or adjustments to reset the system.
If you garage door is lowering then reversing back to the open position there could be something obstructing the sensors.
It will be obvious if it is going bad.