Ive never had 3 lvls of planetary def and been attacked so I dont know if this is a bug or not. I have the original game without DLC (though, that wont be for long). I thought that every lvl of the planeatary def was seperate, so that, when you have researched 3 lvls you get 2+3+4 weapon slots. In the game I just finished, I got attacked for the first time on a planet that had 3 lvls built and only the third lvl of planetary def was active. If this is meant to be then the tech lvl is to high (according to me) for just an extra weapon slot. Should be something more like 2;4;6. If not, then it is bugged.
Enemy of my enemy achievement
I also finished the game in an alliance with the Yoral to achieve the "Enemy of my enemy" steam award but didnt get it. Something wrong?
This has happened to me several times. When you get into a fleet engagement with several carriers, some/all of the fighters turn invisible.