If an Illustrator window is moved and resized via the Accessibility API, then the window widgets will vanish. They will reappear if you manually resize the window (even if only by a pixel).

This issue affects anyone who uses a third-party window manager, such as our app Moom. It was reported by one of our users, and this video is theirs—we don't have Illustrator, so we can't test on our end.

If you watch the video, you'll see the window widgets vanish when the user uses Moom to move the window; they then reappear when they manually resize the window. As third-party apps have to use the Accessibility API to work with other apps' windows, this is a pretty major problem for users of such apps.

https://www.youtube.com/watch?v=EIJ_l5CPSqc

There's nothing we can do about this in our app, it's something Adobe needs to fix in Illustrator. We can work with someone there on a solution if necessary.

I can't report the version of Illustrator or the OS, because as noted, this video comes from one of our users, not from us.