After the mine stage, in the Fallen Shield phase, no enemies except the Scorch cannon holders and a couple of drones that spawn with the first one where present. We tried wiping, restarting the game, and changing group leader, even resetting checkpoints and restarting the dungeon. The video is my partner recording our encounter. Also the ogre boss Phry'Zhia seemed to behave strangely, moving when he didn't have to.
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During the fallen shield enemies only spawn at one location at a time. You have to look around for where the servitor spawns and that will have the enemies.