The most likely cause of that is that the springs that help lift the door and prevent it from closing to fast need to be adjusted or replaced.
Garage door is not closing evenly.
Have a helper steady the ladder.
If the door simply stops short of the floor the likely culprit is the down limit switch.
Repairing your garage door springs can be a dangerous job due to the weight of the door.
Place a stepladder beneath the box portion of the garage door opener.
If your garage door is closing fully and then reversing to open again then it may be due to a problem with the close limit switch.
If your door has a gap on one side or the other when it s closed the problem is most likely due to a break or other issue with one of the extension springs.
When this happens you need to shift it back into position.
Put a ladder under the door to make sure it won t close accidentally while you re working on it.
This can happen when the door has shifted to one side causing it to appear uneven.
When the settings are too high the door senses the floor as an obstruction and immediately opens again after closing.
The most simple and common is door shift.
If the garage door stops look okay but the door is out of plumb not perfectly vertical when closed check the vertical sections of the roller tracks on each side of the door.
If you suspect you need to adjust one or both of the extension.
Do not attempt to do this yourself.
Keep the door open a few feet off the ground as this takes the pressure off the door springs.
In order to fix this you ll want to make small changes to the close limit setting until the door opener knows to stop once the door has reached the floor.
The extension springs are evenly matched and installed to keep the garage door properly aligned so that it runs smoothly throughout the entire length of the track and closes evenly.
There are several things that can cause this.