Thanks for the suggestion.
Adding more save slots or changing the directory may not resolve this problem, but I'll need to work on the saving system eventually, since one slot isn't much.
The model break between updates occurs when the 3D asset is reimported (noticeable traits like NPCs reduced to a wig on the floor, or some characters not showing in the scene, but dialogue still plays).
This bug will technically stop once I no longer need to reimport all the meshes regularly—this process is a real pain. (Adding morph targets, rearranged shader order... etc.)