There are a few things that may cause this behavior.
Camera is installed upside down. The SDI port/BNC connector must be pointing upward on a Standard Helix when shooting. Installing it upside down may cause the Helix to try to turn 180 degrees on start up.
The initial angle/home position for the roll axis is not set to zero. This setting is in the RC tab of the SimpleBGC GUI or on the orientation/calibration screen for the iOS app. You can also manually this roll angle by quickly pressing the Menu button five times and then moving the camera to the correct roll position in the short two second window that follows.
The calibration is off. This could be either the gyro or the accelerometer calibration causing this. If you opted to do the manual roll angle adjustment in step two (rather than doing it in the software), and it is still off by less than 20 degrees, then most likely it is the gyro calibration. Instructions for calibration can be found here for firmware 2.55 or above or here for firmware 2.43 b6 and earlier.