Bahlak stay invisible after a Tornado attack.

I lost the bug ID because forum was not accessible when I encounter the issue.
I'm using spark build so Shock can be a potential trigger, no Electrocute.

As title described, Bahlak become invisible when he cast a tornado attack (after day/night cycle rapidly switches mid-fight), and stay invisible throughout the fight until he cast the tornado attack again, at which point he briefly become visible during casting animation and become invisible again, but doing so seem to reset the pattern and he become visible after second tornado is scattered.

While invisible he still do various attacks and deal damage like normal.

I had exact same issue happen today. See vid of it: https://imgur.com/a/VlBQTlS

Happened to me just now. He didn't cast tornado again so he stayed invisible the rest of the fight. When my sparks would hit, his outline from the lightning effect would be visible.

https://www.youtube.com/watch?v=0bjsgjCRZQQ

Still happening. Just happened to me exactly as described. Only became visible again after it killed me.

Sill happened for me, just after a tornado, he became invisible and I cant see it.

Disappeared after like 30sec maybe, when he decided to make a new tornado. Then he disappeared again after the new tornado

Love to see that after a month, this is still a problem. This boss is hands-down the worst.