EDIT: Updated title.

Taking the dock out of the loop and simply plugging in an HDMI monitor also causes the problem. Below is the syslog from single plug/unplug cycle.

```
$ tail -f /var/log/syslog 
Apr 26 18:54:49 dathon systemd[1]: Starting Hostname Service...
Apr 26 18:54:49 dathon nautilus[7520]: Called "net usershare info" but it failed: Failed to execute child process “net” (No such file or directory)
Apr 26 18:54:49 dathon dbus-daemon[463]: [system] Successfully activated service 'org.freedesktop.hostname1'
Apr 26 18:54:49 dathon systemd[1]: Started Hostname Service.
Apr 26 18:54:49 dathon rtkit-daemon[905]: Supervising 6 threads of 3 processes of 1 users.
Apr 26 18:54:49 dathon rtkit-daemon[905]: message repeated 5 times: [ Supervising 6 threads of 3 processes of 1 users.]
Apr 26 18:54:49 dathon rtkit-daemon[905]: Successfully made thread 7601 of process 7406 owned by '1000' RT at priority 10.
Apr 26 18:54:49 dathon rtkit-daemon[905]: Supervising 7 threads of 4 processes of 1 users.
Apr 26 18:55:02 dathon rtkit-daemon[905]: message repeated 12 times: [ Supervising 7 threads of 4 processes of 1 users.]
Apr 26 18:55:19 dathon systemd[1]: systemd-hostnamed.service: Deactivated successfully.
Apr 26 18:55:35 dathon gnome-shell[1649]: Spurious clutter_actor_allocate called for actor 0x55ebc7aac030/<dashtodockContainer>[<Gjs_ubuntu-dock_ubuntu_com_docking_DashToDock>:0x55ebc7aac030] which isn't a descendent of the stage!
Apr 26 18:55:35 dathon gnome-shell[1649]: Timelines with detached actors are not supported. <dashtodockContainer>[<StBin>:0x55ebc7679c30] in animation of duration 500ms but not on stage.
Apr 26 18:55:35 dathon gnome-shell[1649]: Timelines with detached actors are not supported. <dashtodockContainer>[<StBin>:0x55ebc73bf090] in animation of duration 500ms but not on stage.
Apr 26 18:55:36 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 35 with keysym 35 (keycode e).
Apr 26 18:55:36 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 32 with keysym 32 (keycode b).
Apr 26 18:55:36 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 33 with keysym 33 (keycode c).
Apr 26 18:55:36 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 31 with keysym 31 (keycode a).
Apr 26 18:55:36 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 36 with keysym 36 (keycode f).
Apr 26 18:55:36 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 37 with keysym 37 (keycode 10).
Apr 26 18:55:36 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 38 with keysym 38 (keycode 11).
Apr 26 18:55:36 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 39 with keysym 39 (keycode 12).
Apr 26 18:55:36 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 34 with keysym 34 (keycode d).
Apr 26 18:55:36 dathon gnome-shell[1649]: meta_window_set_stack_position_no_sync: assertion 'window->stack_position >= 0' failed
Apr 26 18:55:46 dathon gnome-shell[1649]: Timelines with detached actors are not supported. <dashtodockContainer>[<StBin>:0x55ebc0ff0520] in animation of duration 500ms but not on stage.
Apr 26 18:55:46 dathon gnome-shell[1649]: st_widget_get_theme_node called on the widget [0x55ebc5e96130 Gjs_ubuntu-dock_ubuntu_com_docking_DashToDock.bottom shrink running-dots fixed extended:insensitive "dashtodockContainer"] which is not in the stage.
Apr 26 18:55:46 dathon gnome-shell[1649]: Spurious clutter_actor_allocate called for actor 0x55ebc5e96130/<dashtodockContainer>[<Gjs_ubuntu-dock_ubuntu_com_docking_DashToDock>:0x55ebc5e96130] which isn't a descendent of the stage!
Apr 26 18:55:46 dathon gnome-shell[1649]: Timelines with detached actors are not supported. <dashtodockContainer>[<StBin>:0x55ebc267e930] in animation of duration 500ms but not on stage.
Apr 26 18:55:46 dathon gnome-shell[1649]: Timelines with detached actors are not supported. <dashtodockContainer>[<StBin>:0x55ebc4435000] in animation of duration 500ms but not on stage.
Apr 26 18:55:47 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 35 with keysym 35 (keycode e).
Apr 26 18:55:47 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 33 with keysym 33 (keycode c).
Apr 26 18:55:47 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 31 with keysym 31 (keycode a).
Apr 26 18:55:47 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 34 with keysym 34 (keycode d).
Apr 26 18:55:47 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 32 with keysym 32 (keycode b).
Apr 26 18:55:47 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 37 with keysym 37 (keycode 10).
Apr 26 18:55:47 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 38 with keysym 38 (keycode 11).
Apr 26 18:55:47 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 36 with keysym 36 (keycode f).
Apr 26 18:55:47 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 39 with keysym 39 (keycode 12).
Apr 26 18:55:59 dathon dbus-daemon[1427]: [session uid=1000 pid=1427] Activating service name='org.gnome.ControlCenter.SearchProvider' requested by ':1.38' (uid=1000 pid=1649 comm="/usr/bin/gnome-shell " label="unconfined")
Apr 26 18:55:59 dathon dbus-daemon[1427]: [session uid=1000 pid=1427] Activating service name='org.gnome.Nautilus' requested by ':1.38' (uid=1000 pid=1649 comm="/usr/bin/gnome-shell " label="unconfined")
Apr 26 18:55:59 dathon dbus-daemon[1427]: [session uid=1000 pid=1427] Activating service name='org.gnome.Calculator.SearchProvider' requested by ':1.38' (uid=1000 pid=1649 comm="/usr/bin/gnome-shell " label="unconfined")
Apr 26 18:55:59 dathon dbus-daemon[1427]: [session uid=1000 pid=1427] Activating service name='org.gnome.Characters.BackgroundService' requested by ':1.38' (uid=1000 pid=1649 comm="/usr/bin/gnome-shell " label="unconfined")
Apr 26 18:55:59 dathon dbus-daemon[1427]: [session uid=1000 pid=1427] Successfully activated service 'org.gnome.ControlCenter.SearchProvider'
Apr 26 18:55:59 dathon dbus-daemon[1427]: [session uid=1000 pid=1427] Successfully activated service 'org.gnome.Nautilus'
Apr 26 18:55:59 dathon dbus-daemon[1427]: [session uid=1000 pid=1427] Successfully activated service 'org.gnome.Characters.BackgroundService'
Apr 26 18:55:59 dathon dbus-daemon[1427]: [session uid=1000 pid=1427] Successfully activated service 'org.gnome.Calculator.SearchProvider'
Apr 26 18:55:59 dathon nautilus[8097]: Connecting to org.freedesktop.Tracker3.Miner.Files
Apr 26 18:55:59 dathon nautilus[8097]: Source ID 161 was not found when attempting to remove it
Apr 26 18:55:59 dathon gnome-shell[1649]: Timelines with detached actors are not supported. <unnamed>[<Gjs_ui_search_ListSearchResult>:0x55ebbe4e6bb0] in animation of duration 100ms but not on stage.
Apr 26 18:56:25 dathon gnome-shell[1649]: Timelines with detached actors are not supported. <dashtodockContainer>[<StBin>:0x55ebbf479430] in animation of duration 500ms but not on stage.
Apr 26 18:56:25 dathon gnome-shell[1649]: Timelines with detached actors are not supported. <dashtodockContainer>[<StBin>:0x55ebc3ff6cf0] in animation of duration 500ms but not on stage.
Apr 26 18:57:17 dathon gnome-shell[1649]: Timelines with detached actors are not supported. <dashtodockContainer>[<StBin>:0x55ebc7c2b440] in animation of duration 500ms but not on stage.
Apr 26 18:57:17 dathon gnome-shell[1649]: meta_monitor_manager_get_logical_monitor_from_number: assertion '(unsigned int) number < g_list_length (manager->logical_monitors)' failed
Apr 26 18:57:17 dathon gnome-shell[1649]: meta_workspace_get_work_area_for_monitor: assertion 'logical_monitor != NULL' failed
Apr 26 18:57:17 dathon gnome-shell[1649]: meta_monitor_manager_get_logical_monitor_from_number: assertion '(unsigned int) number < g_list_length (manager->logical_monitors)' failed
Apr 26 18:57:17 dathon gnome-shell[1649]: meta_workspace_get_work_area_for_monitor: assertion 'logical_monitor != NULL' failed
Apr 26 18:57:17 dathon gnome-shell[1649]: JS ERROR: TypeError: monitor is undefined#012vfunc_allocate@resource:///org/gnome/shell/ui/workspace.js:1042:29#012_prepareMainDash/<@/<email address hidden>/docking.js:2159:18#012vfunc_allocate@resource:///org/gnome/shell/ui/workspacesView.js:555:25#012vfunc_allocate@resource:///org/gnome/shell/ui/workspacesView.js:711:30
Apr 26 18:57:17 dathon gnome-shell[1649]: meta_monitor_manager_get_logical_monitor_from_number: assertion '(unsigned int) number < g_list_length (manager->logical_monitors)' failed
Apr 26 18:57:17 dathon gnome-shell[1649]: meta_workspace_get_work_area_for_monitor: assertion 'logical_monitor != NULL' failed
Apr 26 18:57:17 dathon gnome-shell[1649]: JS ERROR: TypeError: monitor is undefined#012_updateRoundedClipBounds@resource:///org/gnome/shell/ui/workspace.js:1006:9#012_init/<@resource:///org/gnome/shell/ui/workspace.js:983:18
Apr 26 18:57:17 dathon gnome-shell[1649]: meta_monitor_manager_get_logical_monitor_from_number: assertion '(unsigned int) number < g_list_length (manager->logical_monitors)' failed
Apr 26 18:57:17 dathon gnome-shell[1649]: meta_workspace_get_work_area_for_monitor: assertion 'logical_monitor != NULL' failed
Apr 26 18:57:17 dathon gnome-shell[1649]: clutter_actor_allocate: assertion '!isnan (real_allocation.x1) && !isnan (real_allocation.x2) && !isnan (real_allocation.y1) && !isnan (real_allocation.y2)' failed
Apr 26 18:57:17 dathon gnome-shell[1649]: Timelines with detached actors are not supported. <dashtodockContainer>[<StBin>:0x55ebc2beb230] in animation of duration 500ms but not on stage.
Apr 26 18:57:17 dathon gnome-shell[1649]: Timelines with detached actors are not supported. <dashtodockContainer>[<StBin>:0x55ebba806720] in animation of duration 500ms but not on stage.
Apr 26 18:57:17 dathon gnome-shell[1649]: Can't update stage views actor <unnamed>[<Gjs_ui_workspace_Workspace>:0x55ebc75c3f60] is on because it needs an allocation.
Apr 26 18:57:17 dathon gnome-shell[1649]: Can't update stage views actor <unnamed>[<ClutterActor>:0x55ebc4aca9a0] is on because it needs an allocation.
Apr 26 18:57:17 dathon gnome-shell[1649]: meta_background_get_texture: assertion 'monitor_index >= 0 && monitor_index < self->n_monitors' failed
Apr 26 18:57:17 dathon gnome-shell[1649]: meta_display_get_monitor_geometry: assertion 'monitor >= 0 && monitor < n_logical_monitors' failed
Apr 26 18:57:17 dathon gnome-shell[1649]: meta_monitor_manager_get_logical_monitor_from_number: assertion '(unsigned int) number < g_list_length (manager->logical_monitors)' failed
Apr 26 18:57:17 dathon gnome-shell[1649]: meta_workspace_get_work_area_for_monitor: assertion 'logical_monitor != NULL' failed
Apr 26 18:57:17 dathon gnome-shell[1649]: JS ERROR: TypeError: monitor is undefined#012_updateRoundedClipBounds@resource:///org/gnome/shell/ui/workspace.js:1006:9#012_init/<@resource:///org/gnome/shell/ui/workspace.js:983:18
Apr 26 18:57:17 dathon gnome-shell[1649]: meta_monitor_manager_get_logical_monitor_from_number: assertion '(unsigned int) number < g_list_length (manager->logical_monitors)' failed
Apr 26 18:57:17 dathon gnome-shell[1649]: meta_workspace_get_work_area_for_monitor: assertion 'logical_monitor != NULL' failed
Apr 26 18:57:17 dathon gnome-shell[1649]: clutter_actor_allocate: assertion '!isnan (real_allocation.x1) && !isnan (real_allocation.x2) && !isnan (real_allocation.y1) && !isnan (real_allocation.y2)' failed
Apr 26 18:57:17 dathon gnome-shell[1649]: Can't update stage views actor <unnamed>[<Gjs_ui_workspace_Workspace>:0x55ebc75c3f60] is on because it needs an allocation.
Apr 26 18:57:17 dathon gnome-shell[1649]: Can't update stage views actor <unnamed>[<ClutterActor>:0x55ebc4aca9a0] is on because it needs an allocation.
Apr 26 18:57:17 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 31 with keysym 31 (keycode a).
Apr 26 18:57:17 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 34 with keysym 34 (keycode d).
Apr 26 18:57:17 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 35 with keysym 35 (keycode e).
Apr 26 18:57:17 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 33 with keysym 33 (keycode c).
Apr 26 18:57:17 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 37 with keysym 37 (keycode 10).
Apr 26 18:57:17 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 38 with keysym 38 (keycode 11).
Apr 26 18:57:17 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 36 with keysym 36 (keycode f).
Apr 26 18:57:17 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 32 with keysym 32 (keycode b).
Apr 26 18:57:17 dathon gnome-shell[1649]: Window manager warning: Overwriting existing binding of keysym 39 with keysym 39 (keycode 12).
Apr 26 18:57:27 dathon NetworkManager[464]: <info>  [1651013847.0621] manager: NetworkManager state is now CONNECTED_SITE
Apr 26 18:57:27 dathon dbus-daemon[463]: [system] Activating via systemd: service name='org.freedesktop.nm_dispatcher' unit='dbus-org.freedesktop.nm-dispatcher.service' requested by ':1.4' (uid=0 pid=464 comm="/usr/sbin/NetworkManager --no-daemon " label="unconfined")
Apr 26 18:57:27 dathon systemd[1]: Starting Network Manager Script Dispatcher Service...
Apr 26 18:57:27 dathon dbus-daemon[463]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
Apr 26 18:57:27 dathon systemd[1]: Started Network Manager Script Dispatcher Service.
Apr 26 18:57:27 dathon NetworkManager[464]: <info>  [1651013847.1632] manager: NetworkManager state is now CONNECTED_GLOBAL

```