I can't get past the first combat encounter in that quest, because the big shrieker boss won't open. I believe this is because only one Lucent Archivst spawns, when at least two should spawn (I'm stuck on the quest step "Defeat Lucent Archivsts", notice the plural). I've attempted 3 times across two days now to complete this, each time fully clearing that room, and can't get further. Am I missing something or is it bugged?