After testing with my new PCB, I noticed that the BHI360 in sensor fusion mode (using BMM350) running the orientation virtual device has drift far higher than is ok, or is advertised.
It sways about 1.25 degrees every minute. It meets back at a similar point, but no matter what, it will drift +0.65 degrees and then -0.65 degrees, or thereabouts.
What could be causing this? I don't live in a super noisy environment. Has Bosch even refined the sensor fusion for this chip? How is it even possible that a FULL SENSOR FUSION chip could drift 1.25 degrees if the accel and gyro are NOT registering movement?