A couple of days ago we lost power and I had to open the garage door manually. The door did not stay up as it is supposed to. It stay half the way so I had to shove a piece of wood to keep it up and move my car. We hardly ever loose power here (California, USA) so I never bother to look at the springs. Now I was looking at it to plan adding torsion to the springs so the door would stay up and I noticed that the left spring looks unwound (comparing green arrows). It also does not feel hard like the right one. You can see it a bit wavy? I installed the springs myself about 4 years ago. I can easily rewind it but I'm concerned what would happen when I loosen up the bolts (two bolts on each spring pointed to by red arrows). I tried to move the left spring by inserting the handle bar but it is not loose. It wasn't hard doing the install but adding torsion is not without risk.
Any chance the springs are slipping from the cups (ends)?