rare problem

[Ralf Mardorf]

If you should stay with 16.04 and wish to help the developers the
following links could become useful:

https://help.ubuntu.com/community/TroubleShootingGuide
https://help.ubuntu.com/community/LinuxLogFiles
https://www.linux.com/learn/tutorials/752708-linux-commands-for-troubleshooting-linux-graphical-apps-for-beginners

Assumed you need to use a live media, that does not use systemd, you
still could read the binary log file using the strings command:

$ sudo strings /mnt/point_of_ubuntu/var/log/journal/*/system.journal | grep -i message

No chroot or systemd-nspawn is required, you only need to mount the the
partition providing /var/.