If you take two lines and make an X shape and group it, when rotating this shape (say 30%), the bounding box resets to straight up and down (as opposed to rotating with the X shape) so any further scaling of this shape will be off. In this case, the X will become asymmetrical with any further scaling. This is a new bug as previously versions of Illustrator kept the bounding box oriented as it was originally.

This is on a Mac with the latest Illustrator CC.