blades slipping
I do not have one, but from experience I can tell you that if you broke the blades you have also bent the spindle. Take the spindle and the main shaft out and roll them on flat surface. Also, if you've flattened the grips I would change them right away! don't try to fly like this! you don't want one of the blades flying out when hovering! Out of shape grips could also cause the tracking problems.