User forcibly logged out when they login again after Switch User

[clewis]

What I expect to happen:
User session to resume correctly after Switch User

What happens
User session resumes then ends abruptly on first attempt, then succeeds on second attempt

Steps to reproduce
Install lightdm-webkit-greeter
Configure lightdm to use webkit-greeter
Login
Open e.g. a terminal window
Logout -> Switch User
Login to same user
Session resumes (your terminal window will still be open)
After a few moments, session exits abruptly back to webkit-greeter
Login again to same user
Session resumes correctly

This is happening on two fresh Lubuntu 16.04 installs, on different amd64 hardware. It happens 95% of the time with all of the webkit-greeter themes I have tried, including the default. I have not been able to reproduce it with the gtk-greeter. Unfortunately I need the face browser capability of the webkit-greeter for two elderly users who struggle badly with drop-down lists.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: lightdm-webkit-greeter 0.1.2-0ubuntu3
ProcVersionSignature: Ubuntu 4.10.0-40.44~16.04.1-generic 4.10.17
Uname: Linux 4.10.0-40-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.13
Architecture: amd64
CurrentDesktop: LXDE
Date: Mon Nov 27 13:34:28 2017
InstallationDate: Installed on 2017-11-21 (5 days ago)
InstallationMedia: Lubuntu 16.04.3 LTS "Xenial Xerus" - Release amd64 (20170801)
SourcePackage: lightdm-webkit-greeter
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.lightdm.lightdm-webkit-greeter.conf: 2017-11-27T12:42:55.686522