Bug in civil war quest (The Elder Scrolls 5: Skyrim)

Hello! Help, if who faced. In the civil war quest, when it comes to clearing forts or cities, NPCs that mine, that the enemy spam in one place and hang in the textures of each other (3-5 each) characters, this apparently wildly loads the computer and the FPS drops utterly, you play like in slide show. Can anyone come across? How can be cured?
Skyrim AE
I play as an empire
There are mods, but nothing special:

Alternative start
Highlighting unread books
32 skeletons
HD textures of some objects
Open cities
And a couple of small ones
Thank you in advance))