Vaal Temple invisible enemie

Hi i got always a invisible enemie in a viper room in the vaal temple. I can curse him and see his movements but i cant aim him. The room keeps blocked but i cant kill him. Is this a bug?

The Headhunter belt is causing a lot bug with monsters in the Atziri... I have to take it off and put it back on so the monsters "activate and see me" in order to engage and fight them.
I assume it's because i become less visible to those monsters.

Proximal Tangibility
Temporal Bubble
Dread Banner Aura
Hex Aura (Enfeeble / Temporal Chains)
Smoke / Concealment type modifiers
Phasing
Massive Movement Speed Aura (Haste Aura)

Maybe one of them