Opening a file within the visor window causes the visor window to flicker as the file is opened. Once the application is open, the visor window goes away.
Opening a file from within the visor window should keep the visor window visible until the file’s application opens. That newly opened application should then get focus, and the visor window goes away.
I have also seen this behavior, though I haven’t found a way to consistently reproduce it. For me, it also occasionally happens when opening/closing apps, too: the Visor will flash very briefly, sometimes in the middle of the screen.
I have also seen other sorts of random Visor pop-ups (e.g., when an app generates a child window, like a printing dialogue), but I will post about those in a separate thread when I can report how to reproduce those issues. For now, they seem completely random.