Backup fails during export of a script package
During a backup operation, the export of a script package might fail because it refers to an archive file that does not exist.
Backup job 3 of 3 fails if the backup profile in use is configured for component level backup and backup of script packages is enabled, but a script package refers to an archive file that does not exist. It is likely that such a script package is not being used in any deployment, because the deployment would fail. So you might choose to verify that the script package is not being used in your environment, and simply delete it from the catalog.
If you intend to use the script package in a deployment, then you should upload a valid archive file into the script package so that it deploys successfully.
After uploading a valid script archive, or deleting the script package if it is not being used, run the backup operation again.