/usr/bin/gnome-shell:6:g_assertion_message:g_assertion_message_expr:meta_window_unmanage:handle_other_xevent:meta_x11_display_handle_xevent

The Ubuntu Error Tracker has been receiving reports about a problem regarding gnome-shell. This problem was most recently seen with package version 3.34.3-1ubuntu1, the problem page at https://errors.ubuntu.com/problem/3e51baba6960038ed185034581cb83e4dd4776e6 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/.