I think I've discovered a bug?
- Open a game on macOS
- Have another application open full screen
- Drag the game into the application's fullscreen space so it takes up part of it
- Resize the game so it takes up less space (more might also work)
- The game will now go back to windowed mode and be stuck with the resize cursor displaying. It no longer takes inputs, as far as I can tell.
macOS 10.14.4 Mojave, I can provide more info if needed.