just checked this with 1.6 on another machine and it works fine.
Not sure when this bug crept in but can anyone confirm ?
Further tests are showing some weirdness with sun positions even without using ground plane rotation.
The sun and shadow does not seem to be placed where studio indicates
....ok.... in 1.7.1 the sun seems to rotate twice the angle of the ground plane rotation.
If the ground plane is rotated a full 360 degrees the sun rotates 720 degrees which is seen in the viewport.
Any fixes , suggestions or confirmations ?