The FTP and SFTP backup transports do not support transferring metadata, so it is necessary to disable metadata generation when using those transports. Additionally, if you're backing up to a NFS mount, the metadata must be disabled.
Please note, cPanel does not support backup to NFS filesystems. NFS filesystems can cause issues if connections to the server are interrupted.
The only way to disable metadata generation is through the WHM API:
whmapi1 backup_config_set disable_metadata=1