Like Jeremy said, it's easy to torque the bow when trying to let down slowly. I've seen it many times. The trick is to let down quickly, but in a controlling manner. The more reflexed the riser, the shorter the A2A, and the higher the draw weight the more it is apt to happen.

If it's an issue with cam lean or some other bow malfunction you'd be able to see it quite readily. It's normally just operator error.