[BUG] HOTU: Illithid Overlord Room Causing Severe Frame Rate Drop

In Hordes of the Underdark, once entering the Overlord's chamber in the illithid (mind flayer) town, my frame rates will go from 80's to about 20-30. This drop is permanent (I've been all the way back to the main city of Lith My'athar and still experiencing the problem) until I save and reload. Once I reload the frame rate is fine again. I don't even need to restart the client to fix it. I haven't yet completed chapter two, so I can't open it in the Aurora toolset, but I have a feeling this may be an errant script tied to the Overmind that's stuck in an infinite loop or some such.

My specs are as follows:
i7-5820K
16 GB of DDR4 Corsair Dominator Platinum
GeForce 980 Ti, Driver version: 390.77
Samsung EVO 850 SSD
Windows 10 Home 64-bit, 10.0, Build 16299