Hello Everybody

I have a Garage where the door does not close properly. When the door comes down, right side of the door touches the floor a bit earlier than the left side and then left side kind of falls down. It is falling down about one inch on left.
I have posted the video on.

http://www.youtube.com/watch?v=luetCIyZl3k&feature=youtu.be

I called some professional and he could not help much. He could not explain why it is happening or any solution, just took some money saying he tuned the garage and went away.

Please let me know what are the possible reasons and ways to fix it. Any links tips would be appreciated.
One possibility is the house is a bit tilted.
If that is the reason how could the garage door could be balanced?

Thanks a lot.
Raky