Why does rotated (R) shapes, that I copy and duplicate (Cmd+D) around a circle, get disordered?

Hey, guys, i got this problem and it's really bothering me, when I make a shape, like a single rectangle and i want to rotate/duplicate it all 360º around a circle shape, the ones that are at the central parts (0º, 90º, 180º and 270º) always move a bit.

But it isn't all, when I MOVE (or expand something, for example) my groups ALL together, no exclusions, sometimes (almost every time) those same shapes move different than the other objects :/

WHY!? (Although it isn't such a big deal at simple sight, but it is when you try other stuff) Please help me if you know any tip or at least answer: why does this happen? :/

I would like to thank you in advance.