I would check to make sure the arm where the wing nuts you loosened are at, isn't still pulled forward some. I don't know all the proper terms so I'll just say this the best I can. My son's back brakes got stuck on once. When you used them and one of the cables pulled that arm forward, the brakes would work. However, when you let off of them and the cable relaxed, the arm would stay forward until you knocked it back. There was some rust/gunk inside the hole where that arm goes inside the hub(maybe the right term) to spread the brakes out. I had to pull the arm out and clean it and the hole and grease them.