Not sure if this is an issue in Supercharged or in iOS, so forgive me if it's an iOS thing, but have you ever encountered an issue where the file path is reported as null?

It's an iOS thing. Path can be null if the track is not "owned" by the user, such as a track downloaded from Apple Music, which is a streaming service, and record labels don't provide license to Apple to serve those files to third party apps.