In the mission, The Culling, the Undead Elite Guard (Green) and Undead Scourge (Purple) are fighting each other. This did not happen in the OG The Culling and lore wise makes zero sense. Only thing I could think of is this is a bug. I wonder if the Red faction of Undead are also hostile to Undead Elite Guard and Undead Scourge.
Which graphics setting?
I ran through it today without issues. Are you loading from a save checkpoint by chance?
Same thing happened on my end. They must’ve just forgotten to make them allies, since the map is heavily scripted and those two armies are unlikely to come into contact.