>>397875880
Pretty sure the game only ever spawns things on tide or mission select, not while you're in there. You should be able to scout an area or at least try to bait them outside a bit. I cleared the kolhoz train yard by shooting around the double doors nearer castle and then running all the way around to the field side and sneaking in. All the main threats left and gave me just enough opportunity to get in and pop the rift before trying to fight the group properly.