First, it happens to me a few times.
1. Loot on the floor, (possibly leftover from the last group), remains.
2. Enemies aggroed at the beginning of the quest, even before seeing a player character. (This might be caused by their in-fighting)
2-1. Aggored sprit chanter starts summoning, which results in about 10~20 summons at the first encounter.
Summoned ghost uses negative ray.
10~20 beam turrets, it's what they are.
This bug was still there as of yesterday.
it should be properly cleaning up now.