In third person mode. shader will reset. but you can turn on again.
i press F4 key but don't work. it only work in F5 key.

STEPS TO REPRODUCE:
Create a world.
Wait until world created.
Press esc key on your keyboard and then go to options.
Click "Super Secret Settings" button.
Click "Done" and then click 'Back To Game"
Press F5 on your keyboard.
Your shader is now reset.