FPS drop near certain npcs when running MCA

[uberwill]

I have a strange issue apparently related to MCA - when the player character approaches a certain npc in the Assarnatamat Shrine cave framerate drops from 60+ to around 3-4 fps.

(specific npc is _MCA_hag_dunmer00000000, but I can confirm this happens with multiple MCA npcs.)

 

I have tried disabling AI in the console (via the tai function) which did not improve the fps. The next thing I tried was killing the npc, which for some reason 'fixed' the fps drop.

 

Another possible clue is that the npc seems to have an unusually lengthy (streaky) shadow, at least while standing upright. I am not certain if this is the root of the problem, but when I set real time shadows to 'off,' the fps returns to normal.

 

Any clue as to what might be the real problem here? (I mainly ask out of curiosity.)