when xclock is open, gnome alt-tab menu does not show

[themusicgod1]

easy to reproduce
1) run xclock
2) alt-tab within gnome

result: no alt-tab menu, alt-tab seems to be grabbed by xclock somehow.

x11-apps:
  Installed: 7.7+5
  Candidate: 7.7+5

gnome-shell:
  Installed: 3.16.4-0ubuntu1
  Candidate: 3.16.4-0ubuntu1
  Version table:
 *** 3.16.4-0ubuntu1 0
        500 http://ca.archive.ubuntu.com/ubuntu/ wily/universe amd64 Packages
        100 /var/lib/dpkg/status

ubuntu 15.10

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: gnome-shell 3.16.4-0ubuntu1
Uname: Linux 4.1.0-040100rc1-generic x86_64
ApportVersion: 2.19.1-0ubuntu3
Architecture: amd64
CurrentDesktop: GNOME
Date: Tue Oct 27 15:14:23 2015
DisplayManager: gdm
EcryptfsInUse: Yes
GsettingsChanges: b'org.gnome.desktop.interface' b'gtk-im-module' b"'gtk-im-context-simple'"
InstallationDate: Installed on 2014-07-09 (475 days ago)
InstallationMedia: Ubuntu-GNOME 14.10 "Utopic Unicorn" - Alpha amd64 (20140708)
SourcePackage: gnome-shell
UpgradeStatus: No upgrade log present (probably fresh install)

[themusicgod1 (themusicgod1)]

doesn't seem to apply in yakkety (16.10)