Nonbreakable Rek'sai tunnel [GAMEPLAY]

The enemy Rek'sai made a tunnel at our Red buff and it was unable to be removed. Each player tried stepping on it, but nothing happened. The enemy Rek'sai was still able to use thier ultimate to travel to it. The enemy Rek'sai said something about doubling up the tunnels, but I didn't look to see what actually happened.

As mentioned before I'm not sure how to replicate it but I would assume either making a burrow in the same way as the one in the picture, or try making two on top of each other.

I've only seen it occur once.