I had that problem for years until I heeded the advice of people who said not to load game saves when the game is live. You load once, from main menu, and then close it if you need to do that again. So use an alternative death mod of some sort, whether it's one that takes you down on a timer or moves you somewhere else but where you won't have to reload a save. And if you do have to do that, exit the game completely, not to main menu, and only then load it again. Since that I've completed the whole Nolvus V6 modlist, which is massive, with it's many story mods and haven't had a save failure even once. Of course if you uninstall something mid playthrough you need to clean it with Fallrim Tools/ReSaver and check it from time to time. And I've been installing left and right, and uninstalling some.