Found it…
Old version in devkit:
New version in game:
The two NPCs share a gameitem weapon blueprint. They had no reason to duplicate that prior as they don’t hold any important stats and were only used to apply the 10 damage acid buff…
The way they tried to trick players with Steel thewed to still die… is by doing damage via a BUFF instead or regular collision. So they changed the buff on the game item weapon to a different one that does 10k damage… This buff applies on every collision event… (normal damage only applies per group so you’d get a single hit from all that mess from above)…
Bottom line… the Siptah version also got affected because of this and tries to do 10k damage for every collision notify in a group as fast as it can (gets in roughly ~10 instances)
Solution?
If they want to stick with the buff, then they need to create a separate gameitem blueprint for the Kurak version (item template 23410) that applies the new Tidal buff and switch back to the old buff on the gameitem blueprint for template 23403 (siptah version)
@Sarealac this info will probably be useful 
(this is about the Siptah version so… sort-of ended up in the wrong thread, linked it in the relevant one)