Not sure whether the upstream issue, which is several months old, is the same. The present one seems to have kicked in for several users at the same time at the end of June 2021.
It looks like it is somehow connected to Thunderbird. Also see this comment, for one way of reproducing it: https://bugs.launchpad.net/ubuntu/+source/gnome- shell/+bug/1934527/comments/4 I can also confirm that it does not seem to occur if Thunderbird isn't running at all. -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to gnome-shell in Ubuntu. https://bugs.launchpad.net/bugs/1933996 Title: Alt-tab stops switching windows [JS ERROR: TypeError: window is null _createWindowClone@resource:///org/gnome/shell/ui/altTab.js:29:27] Status in GNOME Shell: Unknown Status in gnome-shell package in Ubuntu: Triaged Bug description: When a new Wayland session is created from a login, Alt-tab works as expected to change windows. After sometime Alt-tab fails to do anything (super-tab still works to change applications) and the following error is created in syslog: gnome-shell[777718]: JS ERROR: TypeError: window is null#012_createWindowClone@resource:///org/gnome/shell/ui/altTab.js:29:27#012_init@resource:///org/gnome/shell/ui/altTab.js:1004:34#012_init@resource:///org/gnome/shell/ui/altTab.js:1045:24#012_init@resource:///org/gnome/shell/ui/altTab.js:568:30#012_startSwitcher@resource:///org/gnome/shell/ui/windowManager.js:2069:24 The only workaround I have found is to logout and log back in, however after some time the error repeats itself. Ubuntu 21.04 gnome-shell: Installed: 3.38.4-1ubuntu3~21.04.1 ProblemType: Bug DistroRelease: Ubuntu 21.04 Package: gnome-shell 3.38.4-1ubuntu3~21.04.1 ProcVersionSignature: Ubuntu 5.11.0-22.23-generic 5.11.21 Uname: Linux 5.11.0-22-generic x86_64 ApportVersion: 2.20.11-0ubuntu65.1 Architecture: amd64 CasperMD5CheckResult: unknown CurrentDesktop: ubuntu:GNOME Date: Tue Jun 29 10:53:32 2021 DisplayManager: gdm3 InstallationDate: Installed on 2020-11-11 (230 days ago) InstallationMedia: Ubuntu 20.10 "Groovy Gorilla" - Release amd64 (20201022) RelatedPackageVersions: mutter-common 3.38.4-1ubuntu2 SourcePackage: gnome-shell UpgradeStatus: Upgraded to hirsute on 2021-04-27 (62 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/gnome-shell/+bug/1933996/+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