It seems the boss can take damage with Armor piercing rounds (with no health bar showing the damage taken) but he never dies after his second comeback. Enemies keep spawning, we 6 kept killing and it went on for idk, more than 30 to 45 mins with the boss alone? We tried everything. Waste of valuable time. Btw the boss never comes out of his shield. Another glitch happened where my team went missing all of a sudden and I get into some theater all alone. This happened when we were about to complete the game.