The ride before last involved some wet and slushy conditions. Next time I rode the track was frozen stuck (or so I thought). Eventually got it free by throttling and helping the track along by hand but when it came free there was a noticeable crack. Thought it was just from ice. Now there is a noticeable knocking noise that is cyclical. I let it thaw out in the garage to rule out an ice chunk stuck up in the track. The track wheels are fine. Changed the belt but no change. Nothing seems to be broken underneath. Doesn't make the noise when the I jack the back end up and there isn't any weight on the track...Any ideas?