Sometimes you need to adjust the garage door. This can happen when the door has shifted to one side causing it to appear uneven. When this happens, you need to shift it back into position. There are several things that can cause this. The most simple and common is the door shift. It also depends on the number of years the door has been up, as it could be that the door springs have become worn. The type of door also comes into question, as if it is a drum-driven door, the cable might have come off the roller as well.
Step 1 - Push the Door
Push the door back to adjust the door and get the center-aligned again. It is possible that the vertical track down the side has gone out of alignment and shifted due to a slightly loose lag screw.
By pushing the door back into position, you should have made the vertical track straighten.
Step 2 - Check that it is Straight
Check that the vertical track is straight. If it isn’t 100% straight, slightly loosen the lag screw and straighten it, either using your eye or using a spirit level. When you have positioned it correctly, tighten the lag screw as tight as you can. The door should then hang correctly.
If this is not the problem, it could well be that the springs of the garage door have stretched causing the shift. If that is the case you will have to do a spring replacement instead of simply adjusting the garage door.