This is an aerodynamic occurance, there is nothing wrong with it and nothing you can do about it. When blades are tracked on a real Helo, they are typically tracked at a hover, once IGE and once HOGE, they are tracked again at various speeds... in the case of the CH-47, they are tracked at (if I remember right) 60Kts, 90kts, 120kts, and 140kts. The key is to get the tracking to the best possible tracking for the flying you will do. Now in the case of rc, I would suggest (still new to RC) that you simply track it the best you can.