Perhaps your top blades arent balanced. If you have a digital scale you can figure it out, and add some tape or colored stripes to balance them out. Also, make sure the head is secured to the inner shaft via the screws tightly. Other than that, I dunno.
However, a nice little mod i did for learning was taking the screw that holds the flybar in place OFF. This way, when you do crash, in most cases, it will just pop off instead of bending. Hope this helps.
-Gene