Going to Fullscreen in standalone player causes the screen to become brown, no buttons are visible and white flickers appear.

1. What happened

Making a standalone build, then launching that in fullscreen or using in-game buttons to go to fullscreen does not work (the screen becomes brown, no more UI is visible).

If the game is launched in windowed mode and then button is used to go to Fullscreen, the screen occasionally displays white flickers (see the "5.3 Fullscreen Bug.png"). The flickers seem to mostly occur just after going to fullscreen and when moving the mouse rapidly.

2. How we can reproduce it using the example you attached

• Open the attached project;
• Build and run for OSX in windowed mode;
• Use the in-game "Fullscreen" button to enter Fullscreen;
• See that game has become Fullscreen, but all buttons have dissappeared (they still function normally).

Regression: Works fine in 5.3.2f1