MPU9250 heading is slowly drifting

[It Paradyske]

rtimulibdrive returns stable values:

value 1rate 101: : roll:-0.309687, pitch:-1.506959, yaw:80.975198
value 0rate 101: : roll:-0.293564, pitch:-1.527401, yaw:81.002280
value 1rate 100: : roll:-0.316760, pitch:-1.528041, yaw:81.057994
value 0rate 101: : roll:-0.314997, pitch:-1.498974, yaw:80.771768
value 1rate 101: : roll:-0.305800, pitch:-1.516042, yaw:81.000805
value 0rate 100: : roll:-0.309797, pitch:-1.542201, yaw:81.032517
value 1rate 100: : roll:-0.311155, pitch:-1.543622, yaw:81.026309
value 0rate 101: : roll:-0.301673, pitch:-1.506432, yaw:81.030277
value 1rate 100: : roll:-0.293735, pitch:-1.564458, yaw:80.962829
value 0rate 101: : roll:-0.300660, pitch:-1.530848, yaw:80.862528
value 1rate 101: : roll:-0.321200, pitch:-1.594006, yaw:80.798481
value 0rate 100: : roll:-0.333839, pitch:-1.599711, yaw:80.817776
value 1rate 100: : roll:-0.336110, pitch:-1.563190, yaw:80.951634
value 0rate 101: : roll:-0.350478, pitch:-1.584249, yaw:80.875812
value 1rate 100: : roll:-0.329388, pitch:-1.521089, yaw:80.924013
value 0rate 101: : roll:-0.336932, pitch:-1.548168, yaw:80.955275
value 1rate 101: : roll:-0.342709, pitch:-1.529527, yaw:80.881919
value 0rate 101: : roll:-0.316907, pitch:-1.549707, yaw:80.881925
value 1rate 101: : roll:-0.310421, pitch:-1.575391, yaw:80.868012
value 0rate 101: : roll:-0.295277, pitch:-1.551420, yaw:80.945733
value 1rate 101: : roll:-0.293900, pitch:-1.573405, yaw:80.841019
value 0rate 100: : roll:-0.320140, pitch:-1.526783, yaw:80.801780
value 1rate 101: : roll:-0.316498, pitch:-1.521269, yaw:80.999411
value 0rate 101: : roll:-0.301972, pitch:-1.546375, yaw:80.873272
value 1rate 101: : roll:-0.311741, pitch:-1.521462, yaw:80.918508
value 0rate 101: : roll:-0.307672, pitch:-1.531665, yaw:81.005306
value 1rate 101: : roll:-0.282373, pitch:-1.516774, yaw:80.890955
value 0rate 101: : roll:-0.303756, pitch:-1.502975, yaw:81.016815
value 1rate 101: : roll:-0.322419, pitch:-1.498940, yaw:81.017245
value 0rate 101: : roll:-0.314803, pitch:-1.536608, yaw:81.071163
value 1rate 101: : roll:-0.308038, pitch:-1.538249, yaw:81.108893
value 0rate 101: : roll:-0.318028, pitch:-1.549052, yaw:80.972084
value 1rate 101: : roll:-0.335468, pitch:-1.589224, yaw:81.020728
value 0rate 101: : roll:-0.341171, pitch:-1.564412, yaw:81.032633
value 1rate 101: : roll:-0.353518, pitch:-1.566361, yaw:81.043815
value 0rate 101: : roll:-0.338635, pitch:-1.563627, yaw:80.939354
value 1rate 101: : roll:-0.337559, pitch:-1.584792, yaw:80.940925

It seems that this is not a hardware issue because everybody is getting the same behavior.
It does not seem a rtimulib2 issue either.
I am afraid this is in pypilot side.

Have you tested the latest OP image?
Are you getting correct values?
Do you want me to do any test else?

Same results here, cloned and build https://github.com/RPi-Distro/RTIMULib, and everything is stable.