I'm having a very odd problem, that only just started as I got into a new game including the newest DLC, "Stellar Phenomena" (also including the "Forbidden Worlds DLC").
Now , I am playing as the TEC rebels, I have all research, colonized most planets throughout the game ( I am playing on a Huge Randomly generated map) and I have encountered a problem where rebel forces will jump to one of my planets, and I will instantly loose that planet as one of my colonies and will have to move to re-acquire it, which is proving to be quite a pain.
Here is a couple screenshots, the first is the planet I most recently lost to this bug, the second is one I have recolonized 3 times, quite literally the moment I took the screenshot I lost it again to the 4th group of rebels to phase jump in, as you can see by the 4 groups of rebel ships that have not moved since they phased jumped in, each time instantly taking the planet out of my control.
With all that, I have included my save game in a .zip file including the .savereb and .statsreb in a drop box link: https://www.dropbox.com/s/tjst78wg59mimyo/Save-SinglePlayer.zip
I can upload it in a different format, or just the save game itself if that works better, just let me know and I'll be sure to do just that.
In the picture above, the planets neutral forces are attacking the rebels, which has also happened in all cases of this bug.