I have noticed that, after playing for awhile, when I attack a precursor anomaly or a ship graveyard the battle does not end with the anomaly or ship graveyard destroyed and the "prize" displayed.  Instead, the target is still displayed and the number of enemy ships is displayed (see screen snapshot below). If I save the game, exit, restart the game, and load the saved game, the battles will end normally again.  Sometimes, if I continue to the next turn and attack again, the battle will end normally (but not always).