multiple axis rotation convertion to itself mismatches

[Wasserwecken]

I've tried to convert the rotation of (-0.305291, -6.4072, 91.6871) in the order XZY to the same order again.
This results in rotations shifted by 180°

The same bug happens with any angle greater than 90° or less then -90°
The rotation (91, 91, 91) will fail for any rotation order mapping to itself.

This looks like a minor thing to me, because the resulting angle is basically the same.
Its just rotated in the opposite direction bus resulting in the same position.
By reentering the resulting angle as input ,the rotation matrix and quaterion stays the same.