Yes, I can confirm. This happens on my system as well, and is extremely annoying. It basically means I can’t navigate between Cubase windows with Alt-Tab, or even with mouse clicks, unless I resort to special tricks like first clicking on the mixer window, and then alt-tabbing into the project window to be able to get to it.
I’ve started a whole thread about Alt-Tab issues and window handling in Cubase (on Windows), and it did get the attention of Steinberg developers, so I’m hopeful we’ll see a fix to this at some point.
Here’s that thread for reference. It wouldn’t hurt if you chime in on that thread as well to make Steinberg aware that this is not a user-specific/isolated issue: