The calibration state will change with the change of environment, because it was walking during walking, the surrounding environment was changing, and the change of environment will cause the change of calibration state. When the ambient interference is small, the calibration state will change from below 3 to 3
1. You could try IMU mode instead of 9DOF mode to log data to check heading drift performance, exclude mag influence;
2. Could you get the latest sample to test in your product?
3. As we tested it on your reference board, it worked normally. For the product designed by you, could you give more description or send some doc to us to check it?