i think you might want to take a look at this one Save System / Cloud Save / Encryption / Slot management | Fab
that 96 percent fail on level change is classic save-during-travel race, if you SaveGameToSlot right as you openlevel the object can get torn down mid write
try saving before you call open level and wait for completed, or use async with a gate so you dont fire another save while one is in flight. also dont keep the save object ref across maps, reload it fresh after travel
advanced save system from fab Save System / Cloud Save / Encryption / Slot management | Fab handles this nicer with transaction safe writes + error logging so a fail returns false instead of silently dropping, plus autosave queue so level transitions dont overlap writes