What I meant is that the URL for your upload records are incorrect as
url: "/original/1X/dd758eae1e79c7a2b844d571da9c67ca1df02d39.mp3"
should be
url: "/uploads/default/original/1X/dd758eae1e79c7a2b844d571da9c67ca1df02d39.mp3",
My suggestion for now is to restore from a recent backup and try the migrate_to_s3 script again. If it doesn’t work, avoid running the migrate_from_s3 script so that we can help you debug what is happening.