Ghast skin shadow covers the view after LAN spectating (cheats only in LAN)

I had a map where I opened to LAN to allow cheats and enter spectator mode. I exited the game in spectator mode. After returning to the map I was at the coordinates where I started, but my vision is obstructed by some square shadows, and a shape that is clearly the face of the Ghast. It seems the negative layed out skin of the Ghast appears on the screen as some sort of shader.

It appears on every map. After restarting the game, the artifact disappears.