Now, i'm not a bug tester or anything and in fact, I stumbled across this on accident.
Here is the bug:
When you are sieging an enemy planet and take it over while there are still structures in the air around it. (IE, you sneak in a colony ship/bombing ships to steal the planet away from them without worrying about defense platforms) So after you take an enemy planet and go to the logistics/tactical menu of your new planet, it will tell you that there are no slots available. Because the system is counting the *enemies* logistic/tactical structures as counting against your new planet.
I can't imagine why the enemy structures count against your empire. Is this working as intended or did I actually stumble across a bug?
Great game by the way!