1. On an outdoor map, when one of those nurgle-looking chests spawns on the small ledges, you can't open it for some reason. Also, sometimes mobs are able to shoot through the ledge.
2. When on a mission to silence the guns, sometimes a decimator spawns inside the gun, which makes him untargetable and you can kill it only with AOE
3. When you kill mobs, they occasionally stand still as if they are alive.
4. On a couple of occasions instead of full squad of enemies I encountered a meager one or two heretics.
5. On one assassination mission my designated targets were relatively close to each other and I could finish while exploring only 2/3rds of the map