Volcanic Orb Lagon bug

There is a bug with Volcanic Orb skill during Lagon fight (both campaign and Monolith).

During the first phase everything looks ok, but when we are teleported to the arena, Volcanic Orb don’t do dmg to Lagon’s Tentacles (with a lot of hits). After teleporting back to Lagon I guess it’s somehow bugged even more, because I guess Volcanic Orb hitboxes get bugged like with Tentacles or maybe he just get defense buff after arena stage?

Clip - Twitch