Comment 4 for bug 1651396

To create a new full backup, simply backup to a new location, or move the files in the current location to some other place. Déjà Dup will detect the absence of previous backups and start a new full backup.

The backup location is the directory that stores the duplicity files that Déjà Dup produces (compressed and possibly encrypted duplicity-<full|inc>.<timestamp>.<volumenumber>.<extensions> files). For instance ftp://user@server:port/path/to/backup/location.

You may also want to run the incremental backup that fails, from the command line, with verbose output, to try and understand what leads to that failure, and help triage this bug, because right now we unfortunately don't know enough to reproduce or fix it:

  $ DEJA_DUP_DEBUG=1 deja-dup --backup

As Aaron said Déjà Dup is a good balance between ease of use and reliability. Since it is a front-end to duplicity, I would recommend using duplicity directly for more reliability (see manpage for usage). You would then avoid all the potential front-end bugs.