I am currently playing one of the pre-loaded large maps in beta. One of my planets had it's defenses destroyed, which included hangers and gauss cannons. Once my fleet arrived and destroyed the AI fleet, I went to rebuild my defenses. However, when I clicked on a defense to build it would start "building" it but not allow placement and when it was done I did not have my defense but it took up the allotted tactical slot. I kept repeating this with both hangers and gauss cannons. I would click and it would not allow placement but it would "build" and take a slot but leave me with no actual defense. I ended up with my tactical slots full but with no defensive placements.