upgrades: Manual update of freedombox package interrupted

I saw that a new version of freedombox was available, so I started manual update:

2019-08-31 03:59:16,434 INFO Checking if system is running on battery is skipped. Please install powermgmt-base package to check power status and skip installing updates when the system is running on battery.
2019-08-31 03:59:16,491 INFO Initial blacklist : 
2019-08-31 03:59:16,494 INFO Initial whitelist: 
2019-08-31 03:59:16,497 INFO Starting unattended upgrades script
2019-08-31 03:59:16,499 INFO Allowed origins are: origin=Debian,codename=buster,label=Debian, origin=Debian,codename=buster,label=Debian-Security, o=Debian Backports,a=buster-backports,l=Debian Backports
2019-08-31 03:59:34,058 INFO Packages that will be upgraded: freedombox plinth
2019-08-31 03:59:34,062 INFO Writing dpkg log to /var/log/unattended-upgrades/unattended-upgrades-dpkg.log
2019-08-31 04:01:02,755 WARNING SIGTERM received, will stop
2019-08-31 04:01:10,290 WARNING SIGTERM received, will stop
2019-08-31 04:01:10,391 ERROR Exception happened during upgrade.
Traceback (most recent call last):
  File "/usr/bin/unattended-upgrades", line 610, in cache_commit
    res = cache.commit(install_progress=iprogress)
  File "/usr/lib/python3/dist-packages/apt/cache.py", line 648, in commit
    raise SystemError("installArchives() failed")
SystemError: installArchives() failed
2019-08-31 04:01:12,440 ERROR Exception happened during upgrade.
NoneType: None
2019-08-31 04:01:12,444 ERROR Installing the upgrades failed!
2019-08-31 04:01:12,447 ERROR error message: installArchives() failed
2019-08-31 04:01:12,452 ERROR dpkg returned a error! See /var/log/unattended-upgrades/unattended-upgrades-dpkg.log for details

When I tried to start it again:

2019-08-31 04:05:08,791 INFO Checking if system is running on battery is skipped. Please install powermgmt-base package to check power status and skip installing updates when the system is running on battery.
2019-08-31 04:05:08,834 INFO Initial blacklist : 
2019-08-31 04:05:08,837 INFO Initial whitelist: 
2019-08-31 04:05:08,839 INFO Starting unattended upgrades script
2019-08-31 04:05:08,841 INFO Allowed origins are: origin=Debian,codename=buster,label=Debian, origin=Debian,codename=buster,label=Debian-Security, o=Debian Backports,a=buster-backports,l=Debian Backports
2019-08-31 04:05:08,845 ERROR Lock could not be acquired (another package manager running?)

To solve this, I had to run dpkg --configure -a, and then ran the manual update again.

Contents of /var/log/unattended-upgrades/unattended-upgrades-dpkg.log:

Log started: 2019-08-31  03:59:35
quota not working (qgroup not set)
Preconfiguring packages ...
(Reading database ... 92035 files and directories currently installed.)
Preparing to unpack .../freedombox_19.15~bpo10+1_all.deb ...
Unpacking freedombox (19.15~bpo10+1) over (19.14~bpo10+1) ...
Setting up freedombox (19.15~bpo10+1) ...
Installing new version of config file /etc/apache2/conf-available/matrix-synapse-plinth.conf ...
freedombox-setup-repositories.service is a disabled or a static unit not running, not starting it.
SIGTERM received, will stop
Log ended: 2019-08-31  04:01:10

Log started: 2019-08-31  06:47:32
quota not working (qgroup not set)
(Reading database ... 92044 files and directories currently installed.)
Preparing to unpack .../plinth_19.15~bpo10+1_all.deb ...
Unpacking plinth (19.15~bpo10+1) over (19.14~bpo10+1) ...
Setting up plinth (19.15~bpo10+1) ...
quota not working (qgroup not set)
Log ended: 2019-08-31  06:48:17