This crash doesn't seem to reproduce anymore, and there's no trace of it in e.u.c since version 3.36.4 went in proposed.
❯ apt-cache policy libmutter-6-0 libmutter-6-0: Installed: 3.36.4-0ubuntu0.20.04.2 Candidate: 3.36.4-0ubuntu0.20.04.2 Version table: *** 3.36.4-0ubuntu0.20.04.2 500 500 http://it.archive.ubuntu.com/ubuntu focal-proposed/main amd64 Packages 100 /var/lib/dpkg/status 3.36.3-0ubuntu0.20.04.1 500 500 http://it.archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages 3.36.1-3ubuntu3 500 500 http://it.archive.ubuntu.com/ubuntu focal/main amd64 Packages ** Tags removed: verification-needed verification-needed-focal ** Tags added: verification-done verification-done-focal -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to mutter in Ubuntu. https://bugs.launchpad.net/bugs/1857947 Title: gnome-shell crashed with SIGSEGV in get_top_visible_window_actor() from meta_compositor_sync_stack() from meta_stack_tracker_sync_stack() from stack_tracker_sync_stack_later() from call_later_func() Status in Mutter: Fix Released Status in mutter package in Ubuntu: Fix Released Status in mutter source package in Focal: Fix Committed Bug description: [ Impact ] GNOME Shell crashes [ Test case ] Four-finger gesture seems to trigger it, in any case it can be monitored via - https://errors.ubuntu.com/problem/b0255fcaba794d0a5100e58aeb6f61d2f9d9fe66 [ Regression potential ] Windows might not be closed correctly when requested via delete-events (clicking on clientside decoration close button). ---- The Ubuntu Error Tracker has been receiving reports about a problem regarding gnome-shell. This problem was most recently seen with package version 3.34.1+git20191024-1ubuntu1, the problem page at https://errors.ubuntu.com/problem/b0255fcaba794d0a5100e58aeb6f61d2f9d9fe66 contains more details, including versions of packages affected, stacktrace or traceback, and individual crash reports. If you do not have access to the Ubuntu Error Tracker and are a software developer, you can request it at http://forms.canonical.com/reports/. To manage notifications about this bug go to: https://bugs.launchpad.net/mutter/+bug/1857947/+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