Hi,
If you haven't done so already Make sure everything is straight-inner, outer shaft, flybar, blades are balanced, there is no flashing on any of the plastic linkage balls, or linkage connectors, Is your swashplate level? Is your heli level when you pick it up?. I am new at this, and probably missed some diagnoses, but the latter has helped me fix some problems that I have had. Someone on here will have the solution, they always do!!! Good Luck!!!