6 and 7 Star Darth Vader

From certain point of view, exploiting is possible when there is a bug, but it is not players' responsibility to not exploiting a bug. Instead, it is the game itself glitched to allow such a thing to happen. So the most appropriate way to this problem is not having Vader's stars reduced but to roll back where the vader's star SHOULD be because they didn't complete the achievement at all. Giving them a 5 star vader is like saying they have completed all the achievements in which they obviously didn't.
p.s. I just have a 4 star vader lol