While shooting the wild hunter with Revolver from Immersive Engineering and the bullet hits the wild hunter, and the wild hunter summoned wolves.
Or, fire the Revolver around the wild hunter, the bullet didn't hit the wild hunter but attracted wild hunter's hatred and the wild hunter summoned wolves,
under these 2 circumstances the game crashed instantly.
This bug happened when player is at Creative Mode. I didn't test if Survival Mode will be the same.
Mod version is: ars_nouveau-1.16.5-1.18.6

Here's crash report:
crash-2021-06-19_19.45.41-server.txt

Hello, please try the latest version.