Here is something that must be a bug.
Used a star destroyer to take out a system.
*skip ahead*
Now recreate the star and start making new planets from all the asteroids.
One of the planets had a moon. I send two planet makers over there and start one up.
Click on make planet. And then while it is going through the animation for that (or maybe just before) accidentally click on it again (double click as it where). And when the first animation stops it starts another one.
I look and... one tiny planet, no asteroids. Try running my other one there and it doesn't work, no asteroids.
Looks like I just ate up a planet or potential planet.