Came back to say that until there is a fix, this is probably the best solution-- it's fairly easy to do, it doesn't reset any interactions with NPC in terms of dialogue, butr does cover everything in fog of war again, restores any killed creatures and loot in crates/chests/etc.
This fix does not work as stated. Can someone clarify what missing steps there are? Do I need to re-zip my file? Delete the old save file?
I unzipped my savegame, deleted the files with Raedric, and then launched the game again. Loading my game did absolutely nothing different.
You do not have to unzip it. Treat the savegame file as an archive and open it with 7z and then just deletes the mentioned files. You could try unzip and zip it again once you are done but the first method is less of a hassle.