Uneven lift cables
I have a 16' x 7' old wood garage door with tension springs on a steel rod. The door opener has a hard time closing the door because one side has more tension on the cable then the other side. When the door is up one side has some tension on the cable, the other side is slack.
No springs are broken, when the door is down there is tension on both cables but the door is closed unevenly, one side has a gap.