Iron Citadel - Geonor Transformation: Instant Death

Brief summary:
I keep on attacking on Geonor while he was transforming from phase 1 to phase 2, then I died abruptly while doing so.

Character:
* I have Chaos Inoculation
* 8k ES (4k from surplus)
* 75% all elemental res
* 0% armor
* 66% evasion

Geonor:
* Low hp, roughly 10% remaining while transforming
* No indicator of him attacking