我被要求帮助解决遗留系统上损坏的备份脚本。服务器上有一个脚本文件，它应该每小时运行一次，以将数据库备份到 Rackspace 云。这是结果。
START cf-postgresql-dump ...
Wed 04 Nov 2015 06:49:09 AM EST
Synchronizing remote metadata to local cache...
Copying duplicity-full-signatures.20130622T180407Z.sigtar.gpg to local cache.
Download of 'duplicity-full-signatures.20130622T180407Z.sigtar.gpg' failed (attempt 1): CloudFiles returned: 404 Not Found
Download of 'duplicity-full-signatures.20130622T180407Z.sigtar.gpg' failed (attempt 2): CloudFiles returned: 404 Not Found
Download of 'duplicity-full-signatures.20130622T180407Z.sigtar.gpg' failed (attempt 3): CloudFiles returned: 404 Not Found
Download of 'duplicity-full-signatures.20130622T180407Z.sigtar.gpg' failed (attempt 4): CloudFiles returned: 404 Not Found
Download of 'duplicity-full-signatures.20130622T180407Z.sigtar.gpg' failed (attempt 5): CloudFiles returned: 404 Not Found
Giving up downloading 'duplicity-full-signatures.20130622T180407Z.sigtar.gpg' after 5 attempts
问题的根源是什么，解决方法是什么？正如我所见，我们的备份存储中缺少一个文件，因此我们无法生成增量备份。我对吗？