Just watching your video…do you have a true night time in this system? I’m guessing you’d need to disable the sun during the night hours since game worlds aren’t the physical size of Earth and the sun isn’t that far away from the landscapes, otherwise you’d have secondary lighting coming from beneath your landscape.
It was hard to tell from the video how you handle when the sun is not in the sky (and the moon should be - do you have a moon?).