Mzinchaleft/Grimsever bug

[halogamb]

Here is the account of a bug I just encountered and worked around. I have no mods that edit the location in question, Mzinchaleft exterior.

Took Grimsever quest from Mjoll the Lioness in Riften. (Quest requires going into Mzinchaleft Ruins and finding her greatsword, then returning it to her. I map travbel to mzinchaleft, clear the bandits, a dragon, and go in. I cclear my way through and get to the end, fight the Dwarven Centurion, and pick up the quest greatsword, Grimsever. I try to take the lift up to Skyrim, CTD. Reload, try it a few times, all CTD. I go through blackreach to the Mzinchaleft Lift, take it up, CTD. Tried this a bunch of times, CTD. Reload in Mzinchaleft with the quest sword and console teleport myself out to Whiterun, all fine. Map travel to Mzinchaleft, CTD. The only major thing that changed from entering, when everything was fine, to exiting, when all the CTDs happened, was picking up that quest sword. So I reload where I was when I teleported to Whiterun. I go to Riften, hand in the sword so the quest is com pleted. Map travel back to mzinchaleft, no CTD. Go through Mzinchaleft into blackreach and take the lift up out, no CTD. Not sure how or why but there appeared, at least for me, to be something wrong with the final stage of the Grimsever quest and the exterior of anything Mzinchaleft related. Any insight?

[cfs111]

How many items were you carrying? Any mods that affect followers, swords etc.? How often do you use the console? What is the size of your save file? Do you sort your load order with LOOT?