Citadel full clear bug

Finally got to do my first citadel, just to see that it requires you to clear EVERY mob. That said, I zipped through the map and killed the ice wolf boss and then it said I had 3 mobs left. Swept the map three times and killed 2 last mobs with 1 left. I assume the last mob is the boss and it bugged out because I DO NOT see any more mobs on the map. Sad bug.

Got the same bug twice. absolutely cooked