If your garage door goes up and down in a jerky motion you might have one broken spring on a two spring system.
Manual two spring garage door broken.
Two ladders 6 foot or higher these two ladders serve as stoppers when the roller is fully opened.
Some garage door openers are strong enough to lift a door with only one good spring.
A garage door should not be opened until the spring is repaired.
The garage door may be using a one spring system or a two spring system.
If the roller will not be supported by a stopper it would only shut back since the spring is broken and can no longer support the door s heavy weight.
Even though some garage doors have more than two springs in the operation system.
A garage door that has a broken spring has nothing to support its weight.
The herky jerky motion is especially common with garage doors equipped with extension springs.
All though some openers can lift the door you risk damage to the operator and the door.