The rotation values are not being retrieved correctly

I have loaded a STEP file into the viewer and selected the AIS_InteractiveObject representing a part. For that part, I attached an AIS_Manipulator to enable interactive rotation.

I enabled the rotation axis using:
AIS_ManipulatorMode::AIS_MM_Rotation
To perform rotation, I selected the axis and dragged it using the mouse. The rotation is applied via:
Manipulator->Transform(cx, cy, view);

where cx and cy are the current mouse coordinates.

To compute the transformation applied to the part, I used the following code:
Standard_Real angle;
gp_Trsf transformation = currentObject->Transformation();
gp_Quaternion quaternion = transformation.GetRotation();
angle = quaternion.GetRotationAngle();
angle = (angle * 180.0) / PI; // Convert radians to degrees

The values returned by GetRotationAngle() during interaction are as follows:

Observations:
When rotating clockwise, the angle values progress as:
0, 30, 60, 150, 180, -179, -150, -120, -90, -60, -20

When rotating counterclockwise, the angle values progress as:
0, 30, 60, 90, 120, -121, -150, -179, 180, 150, 120, 90, 60, 30

I observed that the angle sign flips after around ±120°, making the sequence discontinuous and harder to interpret.

Question:
Am I doing something wrong in this approach?
If not, what causes this sign change, and how can I avoid or correct it?