I’m not at all experienced in fixing these but some ideas come to mind: I doubt it’s the spring, that would just control rotation of the main rod unless it somehow bent the rod. Could be the tracks on the side are becoming misaligned. That could be from loose track. That might be hard to tell with the door installed due to weight, someone might know of a way to check this.
You also might need to consider that the floor underneath is sinking on the gap side. Are there any cracks in the garage floor? Any cracks on nearby walls? This can happen naturally or due to a leaking pipe where water underground washes away the supporting sand/dirt under the building.
How do I fix this? Is it the spring or something else? ( imgur.com )
See title. Is it the spring lifting one side off the ground or is it something else like the cable on that side? Thanks for any advice!...