Thanks. prevjournal.txt does seem to show gnome-shell repeatedly failing with:

Jan 07 16:03:33 luis-XPS-15-9560 gnome-shell[2211]: JS ERROR: Error: Requiring NMA, version none: Typelib file for namespace 'NMA' (any version) not found
                                                    @resource:///org/gnome/shell/misc/modemManager.js:4:35
                                                    @resource:///org/gnome/shell/ui/status/network.js:12:22
                                                    _init@resource:///org/gnome/shell/ui/panel.js:726:13
                                                    _ensureIndicator@resource:///org/gnome/shell/ui/panel.js:1069:25
                                                    _updateBox@resource:///org/gnome/shell/ui/panel.js:1080:34
                                                    _updatePanel@resource:///org/gnome/shell/ui/panel.js:1026:14
                                                    _init@resource:///org/gnome/shell/ui/panel.js:835:14
                                                    _initializeUI@resource:///org/gnome/shell/ui/main.js:206:13
                                                    start@resource:///org/gnome/shell/ui/main.js:146:5
                                                    @<main>:1:47
Jan 07 16:03:33 luis-XPS-15-9560 gnome-shell[2211]: Execution of main.js threw exception: Script <main> threw an exception
Jan 07 16:03:33 luis-XPS-15-9560 gnome-shell[2211]: Attempting to call back into JSAPI during the sweeping phase of GC. This is most likely caused by not destroying a Clutter actor or Gtk+ widget with ::destroy signals connected, but can also be caused by using the destroy(), dispose(), or remove() vfuncs. Because it would crash the application, it has been blocked and the JS callback not invoked.
Jan 07 16:03:33 luis-XPS-15-9560 org.gnome.Shell.desktop[2211]: == Stack trace for context 0x5617ef98b780 ==
Jan 07 16:03:33 luis-XPS-15-9560 gnome-shell[2211]: The offending signal was destroy on Gjs_ui_panel_AggregateMenu 0x5617efc96c60.

-----------------------

Jan 07 16:03:37 luis-XPS-15-9560 gnome-shell[2645]: JS ERROR: Error: Requiring NMA, version none: Typelib file for namespace 'NMA' (any version) not found
                                                    @resource:///org/gnome/shell/misc/modemManager.js:4:35
                                                    @resource:///org/gnome/shell/ui/status/network.js:12:22
                                                    _init@resource:///org/gnome/shell/ui/panel.js:726:13
                                                    _ensureIndicator@resource:///org/gnome/shell/ui/panel.js:1069:25
                                                    _updateBox@resource:///org/gnome/shell/ui/panel.js:1080:34
                                                    _updatePanel@resource:///org/gnome/shell/ui/panel.js:1026:14
                                                    _init@resource:///org/gnome/shell/ui/panel.js:835:14
                                                    _initializeUI@resource:///org/gnome/shell/ui/main.js:206:13
                                                    start@resource:///org/gnome/shell/ui/main.js:146:5
                                                    @<main>:1:47
Jan 07 16:03:37 luis-XPS-15-9560 gnome-shell[2645]: Execution of main.js threw exception: Script <main> threw an exception
Jan 07 16:03:37 luis-XPS-15-9560 gnome-shell[2645]: Attempting to call back into JSAPI during the sweeping phase of GC. This is most likely caused by not destroying a Clutter actor or Gtk+ widget with ::destroy signals connected, but can also be caused by using the destroy(), dispose(), or remove() vfuncs. Because it would crash the application, it has been blocked and the JS callback not invoked.
Jan 07 16:03:37 luis-XPS-15-9560 gnome-shell[2645]: The offending signal was destroy on Gjs_ui_panel_AggregateMenu 0x5637c66ffae0.
Jan 07 16:03:37 luis-XPS-15-9560 org.gnome.Shell.desktop[2645]: == Stack trace for context 0x5637c4526b50 ==