I get the same disjointed sun with its target when i open your scene, however it jumps back to its target as soon as move either the sun, or the target. Saving the scene and opening it again makes the issue re-appear. I also tried to create a new sun and it acts as expected. Attaching your scene with added new sun (Corona sun003), just to see how it behaves on your side.
I don't have any solutions to this issue, other than try to delete your 3ds Max ENU folder and see if that helps. Don't forget to make a copy, since nuking that folder will wipe out all your customization!