My garage door is a 6 yr old aluminum double width door. I have been running a craftsman 1/2 hp opener for the same 6 yrs.

Today I opened the door fine. When I went to close it, it stopped and went back up. Tried several times, same thing. I unlatched the opener and tried manually to close the door. I saw that it was starting to bucked in the center. When I got the door down, I noticed that the top was about 6-8 inches away from the garage leaving a large gap.

I measured the distance between the rails, top, middle & bottom and they are fine.

Any suggestions??

Obviously there is some binding in the rails or wheels and that must be found and fixed. Inspect the rail mounting brackets and the wheel brackets for any bright shinny scratches that would tell you if something slipped. Come back and tell us what you found.