Copper citadel bug instant kill me after I finished the boss(not tornado)

After 33 days of searching, I found my first citadel, kill the boss and instantly die without any attack or spell

https://www.youtube.com/watch?v=rc3a9Gd34oE

I record it.

Just had basically the same thing happen to me in my stone citadel with Doryani just with a giant lightning bolt after he died, I got "quest completion" and all the loot popped out, then my character just exploded now my map says I failed the citadel.

Same thing just happened to me. Searching everywhere for what happened. I was just dropping a portal to get back to the hideout when the lightning struck> Did you find out what it was?