Fixing a bi-fold door
The problem with one side of my door was that the top pin was loose. This allowed too much play in the track and the pin would hang up in the track and was a real bear to close after you opened the door all the way. You had to wiggle and wiggle and coax it do get the pin past one spot in the track.
Looking at the top of the door and the pin, I saw that the years of wiggling and yanking on the door had enlarged the hole that the pin mount was in. I pulled the mount, taped some pieces of toothpick around the base of the mount til it fit snugly and put it back in.