Thanks for reporting back. I was hoping fullscreen -> minimize -> restore -> gray was fixed! 🙁 It should restore as non-fullscreen, as it seems to do for you, but it should draw the app, not just show gray. We have tried something new in 3.7.54-beta, can you try there? Also in 3.7.54-beta maximize with an auto hiding taskbar avoids being fullscreen by making the window 1px shorter.
How about fullscreen -> alt+tab? I've seen odd behavior with it, like the first time it leaves fullscreen when the app loses focus, but subsequent times it doesn't. Windows handling of undecorated windows sized to the screen is really odd and our control of it feels like voodoo.