Rek'Sai Invulnerable Tunnel Bug (Twisted Treeline)

It occurred when I took the tunnel and knocked Tahm Kench up right as he was finishing clearing the tunnel. I forgot to include footage of them trying to clear the tunnel after that but they couldn't - it did nothing when they stood on it (didn't even make breaking animation anymore).

As shown in the video, it functioned just like a normal tunnel but couldn't be cleared and didn't have a time limit.