At the moment I have a huge Invader fleet in the system next door to Sol, it has been there for decades and destroyed numerous of my warships and several exceptionally stupid freighters. But it and every reinforcement ship are sitting in orbit over a world with no population, or installations and have been for years. I did have an outpost on the planet but I deleted it ages ago, I have SM'd in a sensor ship nearby which confirmed nothing on the planet showed up on passive or active sensors before exploding. Any idea why they are having this group hug there? The Wormhole and any JP are not anywhere near, and in fact some of my crazy freighters keep navigating the system to visit the next one up the chain were the ruins of an allied NPR are and the Invaders ignore them, perhaps they are beyond sensor range but thats hard to tell