update-manager and unattended-upgrades failure

[bedfojo]

A series of issues about update-manager and unattended-upgrade. I have set the system to:
- automatically check for update daily
- when there are security updates, download and install them automatically
- when there are other updates, display them immediately.

What occurs:

(1) unattended-upgrade runs on boot but systematically its log states every day that: "No packages found that can be upgraded unattended and no pending auto-removals" even where there are security updates to install.

(2) update-manager appears not to refresh the cache automatically after boot.

(3) when the cache is manually refreshed so there are updates, update-manager runs after a subsequent boot and appears in the panel. However clicking on it leads it to simply disappear.

(4) update-manager will not launch from the menu. When launched from a terminal it runs correctly, refreshes the cache and will install updates.

No crash reports, nothing obvious in log files.

Ubuntu-MATE 16.10 clean install, fully updated.

[bedfojo (bedfojo)]

Other similar reports:
https://ubuntuforums.org/showthread.php?t=2339387

[bedfojo (bedfojo)]

Also:
https://ubuntuforums.org/showthread.php?t=2330407

[bedfojo (bedfojo)]

And now an error message in the unattended-upgrades log file:

2016-12-08 20:47:28,042 INFO Allowed origins are: ['o=Ubuntu,a=yakkety', 'o=Ubuntu,a=yakkety-security']
2016-12-08 20:47:46,867 ERROR An error occurred: 'Could not resolve 'security.ubuntu.com''
2016-12-08 20:47:46,868 ERROR The URI 'http://security.ubuntu.com/ubuntu/pool/main/g/ghostscript/ghostscript-x_9.19~dfsg+1-0ubuntu6.3_amd64.deb' failed to download, aborting

Looks like it tries to run before the network is up.

[Launchpad Janitor (janitor)]

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

[bedfojo (bedfojo)]

Additional info:
on one occasion I have the following in .xsession-errors
debconf: DbDriver "passwords" warning: could not open /var/cache/debconf/passwords.dat: Permission denied

Further additional info:
manually refreshing the cache then manually running unattended-upgrades works.

I deduce from this that the cache is not updating automatically.

[bedfojo (bedfojo)]

Point (3) of the above can be worked around by running Marco as window manager rather than compiz. Looks like several different issues here.