Hi,
I have found two small bugs in the CSS Tidy feature.
1. In @charset "UTF-8"; it removes the space after charset (@charset"UTF-8" so it does not validate in the CSS Validator.

2. In a Media Query such as,
@media screen and (min-width: 480px) {
}
It removes the space between and, and before (, so it does not validate and does not work correctly in some browsers.
@media screen and(min-width: 480px) {
}

I would open a support topic so the CC gurus can get more info from you.