backup failed with an unknown error

[Dan]

This is happening every time the backup is run. Whether I run it manually, or it runs automatically.

It starts the backup process, but after a while it stops and shows this error title:
Failed with an unknown error.

With the following message:
Traceback (most recent call last):
  File "/usr/bin/duplicity", line 1411, in <module>
    with_tempdir(main)
  File "/usr/bin/duplicity", line 1404, in with_tempdir
    fn()
  File "/usr/bin/duplicity", line 1338, in main
    restore(col_stats)
  File "/usr/bin/duplicity", line 632, in restore
    restore_get_patched_rop_iter(col_stats)):
  File "/usr/lib/python2.7/dist-packages/duplicity/patchdir.py", line 526, in Write_ROPaths
    for ropath in rop_iter:
  File "/usr/lib/python2.7/dist-packages/duplicity/patchdir.py", line 499, in integrate_patch_iters
    final_ropath = patch_seq2ropath( normalize_ps( patch_seq ) )
  File "/usr/lib/python2.7/dist-packages/duplicity/patchdir.py", line 463, in patch_seq2ropath
    assert first.difftype != "diff", patch_seq
AssertionError: [(('README',) reg), (('README',) reg), (('README',) reg)]

Some more info:
 - My backup location is on another internal HDD drive. (I checked every time the backup is running, the HDD was mounted)
 - Data being backed-up is my home folder ( /home/dan ), while some of its subfolders are excluded.
 - /home is on a partition of its own
 - /home partition is on an SSD drive (The SSD drive is split in 2 partitions, second one is / )
 - Using Ubuntu 13.04

$ apt-cache policy deja-dup
deja-dup:
  Installed: 26.0-0ubuntu1
  Candidate: 26.0-0ubuntu1
  Version table:
 *** 26.0-0ubuntu1 0
        500 http://lb.archive.ubuntu.com/ubuntu/ raring/main amd64 Packages
        100 /var/lib/dpkg/status

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: deja-dup 26.0-0ubuntu1
ProcVersionSignature: Ubuntu 3.8.0-30.44-generic 3.8.13.6
Uname: Linux 3.8.0-30-generic x86_64
ApportVersion: 2.9.2-0ubuntu8.3
Architecture: amd64
Date: Thu Oct 3 14:23:09 2013
ExecutablePath: /usr/bin/deja-dup
InstallationDate: Installed on 2012-07-14 (445 days ago)
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
MarkForUpload: True
SourcePackage: deja-dup
UpgradeStatus: Upgraded to raring on 2013-04-26 (160 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.