Light is attached to the model when you rotate it. This is the default behaviour or when you move the Rotation X to any position. The light is fixed relative to the model no matter how you rotate the model (or the camera around the model).
BUT when you change the setting for the Y Rotation something strange happens: When you rotate the model the light is no longer fixed to the model but will move to the opposite side.
You can see in this screenrecording what happens.
I guess it’s something like a sign error and should be not very difficult to fix.