Hm. Which grafics card are you using ? Since i adapted this from the Nvida Flex Demos, perhaps thats something unique to Nvidia ? On the other side, i don´t think it is limited to this grafics card. Hm. Perhaps the reparent for the material instance is broken or you need to set up some values.
IMPORTANT EDIT/NOTE : And its broken if you use it on resized Editor window. Hit F11 to see the window in full screen to see it without buffer glitch.