Two days ago I was riding at the local pit, when i saw a dollar bill on the ground , so i parked my quad next to it (on a hill), and put on the parking break, and let off the foot break. I immediatley started rolling backwards,wonndering why.??? I turned the parking break off, and then back on. Same happened. i looked at the cable that attaches the lever to see if it got detatched, but it didn't, and it looks fine. It even tightens when i tun the lever. I was just wondering, whats the problem??