The point at which upgrade stops is after hitting bionic-backports. Here
are the logs from screen:
Some third party entries in your sources.list were disabled. You can
re-enable them after the upgrade with the 'software-properties' tool
or your package manager.
To continue please press
Public bug reported:
$ lsb_release -rd'
Description:Ubuntu 16.04.5 LTS
Release:16.04
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubuntu-release-upgrader-core 1:16.04.25
ProcVersionSignature: Ubuntu 4.4.0-138.164-generic 4.4.155
Uname: Linux 4.4.0-138-generic x86_64
