Sometimes an alien fleet will approach one of my planets, and then just stop before they get there. They hang out nearby for many turns.



I thought maybe their fleet was bugged out, and so I moved my defenders to another job. Guess what? Yep, suddenly they decided now is the right time to invade my defenseless planet.



But this is not a behavior I can do.

It is a bug that is probably due to the same reasons the AI is capable of moving ships during your turn or even at your turns end.