Maintain portal cube item shape?

I managed to spawn a cube shaped portal item using craftbook, but the cube only maintains its shape for a few seconds before morphing into the regular flat portal item. I'd like to use the hovering portal cube item as a display item for buying an extra life in my shelf shop. Is there a way to force portal cubes to keep their shape, or is this a client side thing?










Cube can be created by restarting both server and clien and quickly spawn the portal after login. Placing it does create a flat portal piece though.