We think that this might be some interaction between Dorico, the UI framework that Dorico is using (Qt) and the operating system’s “Ease of Access” features (things like Narrator, Magnifier etc.). Are you using any of Windows’ accessibility features? If so, is it possible to try turning them off one by one to see if you can work out whether one is triggering the problem? This is just as a diagnostic step - I’m not suggesting that it’s a permanent solution.