I can agree with bubbagates on what he said. What the manual says to use for high rates is what need to use. I have had the same issue with mine and all in all was due to, too much deflection. After i decreased the rates and reset some of my expo it is an IMAC machine. It will complete the basic class with good success. Pilot factor being the limiting part.
If it keeps on snapping to one side check your lateral balance to be sure everything is ok. Once you get the plan trimmed out correctly, It will fly very well.