Trusty → Xenial upgrade window vanishes with no crash

STEPS:
1. Install trusty .4 on a system/vm
2. Update
3. reboot
4. Hit Alt+F2
5. Type update-manager -d
6. You are invited to upgrade after that the window disappears and it is impossible to track if it completed

EXPECTED:
I expect to see the window at all times as the system upgrades

ACTUAL:
After you click on upgrade the update-manager window just disappears
Looking at top there is a Command reading xenial that is running at 100%cpu and doesn't stop.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.8
ProcVersionSignature: Ubuntu 4.2.0-30.35~14.04.1-generic 4.2.8-ckt3
Uname: Linux 4.2.0-30-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.19
Architecture: amd64
CrashDB: ubuntu
Date: Tue Feb 23 14:51:08 2016
InstallationDate: Installed on 2016-02-18 (4 days ago)
InstallationMedia: Ubuntu 14.04.4 LTS "Trusty Tahr" - Release amd64 (20160217.1)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_GB:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
Symptom: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2016-02-23 (0 days ago)