Hey there, someone else had the same issues (which I also run into) and this fixed it for me
Epic - there are a few threads like this (eg Unexpected behavior with SaveGame - Editor Scripting - Unreal Engine Forums), it seems like the SaveGameToSlot and related functions in UGameplayStatics maybe should be ignoring default deltas by default or at least give us a bool flag to make it do that, instead of having to rewrite those functions again? Its a very subtle error that could easily be missed and its not something most would expect would be an issue.