I can't change the proportions of my objects (scaling doesn't work like it should)

I'm sorry, English isn'y my first language. But I assume there's a bug in the latest update. Because I've been having a problem and I just removed the latest version of Illustrator, installed an older version, and the issue is gone.

I can't scale/change the side of objects how I want them to. If I want to exchange only the width, but not the height, for example. So I change the settings for the width, but it automatically scales the height to proportion. I don't want it scaled to proportion, I only want to change what I told Illustrator to change. The chain is unlinked, I did everything right. I let my colleague double check everything as well. We checked and unchecked everything one by one to see if it would make a difference. But I just can't change the width separately from the height (and vise versa). Like I said: the issue was gone when I removed the latest version from Illustrator and installed an older version. Everything works perfects in the older version.