Hi Quentin,
The manual sun position doesn’t appear to be working you are correct. The sun is not aligning with the lighting halo and is remaining static. We have logged this internally and will hopefully get this fixed and amended as soon as we can.
 
For now a potential work around could be altering the origin latitude, origin longitude and origin heading settings within the sequence actor, and using that to alter the height and direction of your sun within the scene. It sadly wont offer the level of control the manual positioning of sky keyframe control would offer, but may working in your use-case.
 
Chris