Manually extracting files from a Plesk backup

Plesk 12.5.30 Update #56
Ubuntu 14.04.5

I'm struggling to rescue some files from a Plesk backup, we do a weekly backup to an external FTP server, the files are split at 2GB in size.

When I try and restore the subscription it eventually fails, in the pmmcli.log is: <errmsg>Unable to export file as file: FTP network error</errmsg>

So maybe in future I should reduce the file size to 512MB so that it's less likely for the transfer to fail, but right now I need to extract some files and get a...

Manually extracting files from a Plesk backup