I had the same thing happen to My hoyt vortec. I didn't even draw it back. I went to go shooting one day, and the string was off of the bottom cam, and was barely holding the bow together. It was resting on the axle. I took it to the pro shop, and the bottom cam was all screwed up. The thing was like leaning to the right big time. I bought the bow brand new, and it was only 2 weeks old. It got sent back to hoyt and they fixed it. They tried saying I dry fired it, and they were refusing to fix it at first, but finally they did. I've never had a problem since. Maybe You have a cam leaning or something?