Issue 750405 is not fixed.

It's very reproducible in betas 19, 20, and 21.
This renders both Game and Scene view inoperable until until the editor is restarted or a new Window > Layout is selected... it also dumps random junk from VRAM (like random scraps from Terminal.app thats also visible) into the Scene/Game region of the editor window if you resize that area.... I can't figure out what causes it... it just pops up seemingly randomly, but very frequently.