thanks Robert, I can confirm that this patch applied on the current xenial package fixes the issue
** Changed in: lightdm (Ubuntu) Status: Confirmed => In Progress -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to lightdm in Ubuntu. https://bugs.launchpad.net/bugs/1605117 Title: LightDM tray items disappear after logout Status in Light Display Manager: Confirmed Status in lightdm package in Ubuntu: In Progress Bug description: LightDM tray items disappear after logout Steps to reproduce: 1) install latest LightDM updates (reboot) 2) login 3) logout Downgrading to LightDM 1.18.1-0ubuntu1 fix problem ProblemType: Bug DistroRelease: Ubuntu 16.04 Package: lightdm 1.18.2-0ubuntu1 ProcVersionSignature: Ubuntu 4.4.0-31.50-generic 4.4.13 Uname: Linux 4.4.0-31-generic i686 ApportVersion: 2.20.1-0ubuntu2.1 Architecture: i386 CurrentDesktop: Unity Date: Thu Jul 21 10:57:44 2016 InstallationDate: Installed on 2016-05-23 (58 days ago) InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release i386 (20160420.1) SourcePackage: lightdm UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/lightdm/+bug/1605117/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp