It is possible that the vertical track down the side has gone out of alignment and shifted due to a slightly loose lag screw.
How to adjust how far a garage door closes.
Open the garage door and watch it closely as it opens.
1 you can align the track with the door itself so that the rollers work properly.
Push the door back to adjust the door and get the center aligned again.
By pushing the door back into position you should have made the vertical track straighten.
If the door was closing too quickly move the spring to the next higher hole on the bracket.
Install a garage door threshold.
Have a helper steady the ladder.
This will help you create a flat and level surface so the gap will close.
These limits must be set correctly for the door height to have a proper seal as well as to allow for adequate clearance.
These may be on the side of the box but are usually at the rear.
Once the spring is free of tension remove from its track hanger.
How to do a simple adjustment on a garage door opener.
You may need a flashlight.
If there s a slight gap at the bottom of your garage door then a garage door threshold is a great option.
2 you can adjust the track so that the door aligns with the weatherstripping.
Check that it is straight.
Look for two limit adjustment screws.
There are two ways that you can adjust garage door track.
Identify the switches by the up or open.
Adjust the springs on both sides of the door the same way.
With a screwdriver adjust these screws.
Each garage door opener has limits which control the opening and closing heights of the door.
When the garage door opens about halfway or 5 feet from the ground and stops the up limit switch needs to be adjusted.
To adjust your door close force use a step ladder to access your door closer.
If it was opening too quickly move it to the next lower hole.
Place a stepladder beneath the box portion of the garage door opener.
Find the limit switch and the adjustment screws that will allow you to adjust the position where your door stops when it closes.
A related topic would be adjusting garage door springs.
How to adjust a garage door to close completely.