With mods a rather common occurrence is when the player is using a mod made from a future update,
for instance if your game-pack is set too update 1.3 then a mod made on the current up to date version 1.5 will inevitably have trouble with running the scripts that have been changed since said update
im not sure if this is your problem but it is a solution as when you update too the current game-pack then everything technically should work without an issue,
however if you are all up too date then it could be a corrupted sav file if this is the case then you will have too start-over on a different save
hope this helped
It sounds like a corrupted game save. I'd recommend going back to a save before entering a dungeon. Corrupted save games have happened to me in Oblivion, and it sounds like what you described. To avoid corrupted saved games make a fresh save (meaning don't save over existing saved games, but create a new one).
Mod conflicts because of wrong load orders have caused this many times for me, and I mod Bethesda games for a long time now, I haven't even had a corrupted save game except for one and when you have one it just says it's corrupted when loading it. Corrupted saves don't even load so this isn't the issue.
I've had issues like the one he described without any mods running at the time. It may not be a "save", but from the "Autosave" of entering the dungeon to the end of that dungeon something happened to cause an error of some type which cause the game to corrupt, which caused a crash at the exterior loading screen (the exit of the dungeon). If he had saved inside the dungeon where this error occurred there would be a high chance that the save he would create would be a corrupt save.
The reason why I believe it's not a mod issue is because he mentions loading to a previous save with no issues at all. Mod issues are pretty consistant, unlike game errors and corrupt saves.
In conclusion, when I played my first few games without mods I've experienced the issued he described in Skyrim, just like in Oblivion. Somehow the issue always solved itself when I reloaded to a previous save, and then made a fresh save. If that's not dealing with game corruption and corrupted saves, I don't know what is. It sure wasn't a mod issue.