My EVO does not fly in a straight line. In my experience this indicates a compass calibration issue. The problem is that when I try to follow the calibration instructions, the calibration fails. The rear LED never turn solid green they flash and when I do the second half I get solid red which indicates failure. Yes I am in an open field , no watch, keys, cell phone ETC. I have done this several times, using the app and using the controller. Any ideas?