We specify the orientation repeatability in our orientation performance specification, where it is called Roll/Pitch static accuracy. See the table below. This accuracy is a result of the accelerometer bias and the estimations in the Xsens sensor fusion algorithm (XKF).
The yaw accuracy depends on the magnetic field, which can be distorted in applications. The yaw repeatibility is 1.0 deg in a homogeneous and undistorted magnetic field.
For reference or more information please see the MTi User Manual.