Thanks for the new update of the sun/star rotation. However at mid-day and mid-night the sun and stars is still changing direction in a weird way. Much much better than before but unfortunately In my game you need to follow the stars and I need it quite realistic 
However I just removed the entire (quite complex) day/night cycle and added a very simple “add local rotation” node which makes the rotation perfect. (Not sure why you choose to make the sun rotate with a set curve?)
But I have another issue, when the sun is moving there is a weird effect where the sun and its lensflare is “flickering”. It can be seen the first seconds in your video:
I have no idea why this is and it doesnt look very nice…