Ubuntu 20.04 - Failed to start GNOME Shell on X11

Today I began to have a problem with my PC: whenever I turn the screen off and on again, I get a blank screen with a "something went wrong" message that forces me to restart session. I restart it succesfully but the problem is still there.

Also today I installed these upgrades:

facundo@razorback:~$ awk '$1=="2020-07-22" && $3=="upgrade"' /var/log/dpkg.log
2020-07-22 13:22:48 upgrade base-files:amd64 11ubuntu5 11ubuntu5.1
2020-07-22 13:22:52 upgrade python3.8-dev:amd64 3.8.2-1ubuntu1.1 3.8.2-1ubuntu1.2
2020-07-22 13:22:52 upgrade libpython3.8-dev:amd64 3.8.2-1ubuntu1.1 3.8.2-1ubuntu1.2
2020-07-22 13:22:53 upgrade libpython3.8:amd64 3.8.2-1ubuntu1.1 3.8.2-1ubuntu1.2
2020-07-22 13:22:54 upgrade python3.8-venv:amd64 3.8.2-1ubuntu1.1 3.8.2-1ubuntu1.2
2020-07-22 13:22:55 upgrade python3.8:amd64 3.8.2-1ubuntu1.1 3.8.2-1ubuntu1.2
2020-07-22 13:22:56 upgrade libpython3.8-stdlib:amd64 3.8.2-1ubuntu1.1 3.8.2-1ubuntu1.2
2020-07-22 13:22:57 upgrade python3.8-minimal:amd64 3.8.2-1ubuntu1.1 3.8.2-1ubuntu1.2
2020-07-22 13:22:58 upgrade libpython3.8-minimal:amd64 3.8.2-1ubuntu1.1 3.8.2-1ubuntu1.2
2020-07-22 13:22:59 upgrade libpulse-dev:amd64 1:13.99.1-1ubuntu3.4 1:13.99.1-1ubuntu3.5
2020-07-22 13:23:00 upgrade libpulse-mainloop-glib0:amd64 1:13.99.1-1ubuntu3.4 1:13.99.1-1ubuntu3.5
2020-07-22 13:23:01 upgrade libpulsedsp:amd64 1:13.99.1-1ubuntu3.4 1:13.99.1-1ubuntu3.5
2020-07-22 13:23:01 upgrade pulseaudio-utils:amd64 1:13.99.1-1ubuntu3.4 1:13.99.1-1ubuntu3.5
2020-07-22 13:23:02 upgrade pulseaudio-module-bluetooth:amd64 1:13.99.1-1ubuntu3.4 1:13.99.1-1ubuntu3.5
2020-07-22 13:23:03 upgrade pulseaudio:amd64 1:13.99.1-1ubuntu3.4 1:13.99.1-1ubuntu3.5
2020-07-22 13:23:05 upgrade libpulse0:amd64 1:13.99.1-1ubuntu3.4 1:13.99.1-1ubuntu3.5
2020-07-22 13:23:08 upgrade ubuntu-drivers-common:amd64 1:0.8.1.1 1:0.8.4~0.20.04.1
2020-07-22 13:23:09 upgrade sudo:amd64 1.8.31-1ubuntu1 1.8.31-1ubuntu1.1
2020-07-22 13:23:11 upgrade ubuntu-release-upgrader-gtk:all 1:20.04.21 1:20.04.23
2020-07-22 13:23:12 upgrade ubuntu-release-upgrader-core:all 1:20.04.21 1:20.04.23
2020-07-22 13:23:13 upgrade python3-distupgrade:all 1:20.04.21 1:20.04.23
2020-07-22 13:23:13 upgrade evince-common:all 3.36.5-0ubuntu1 3.36.7-0ubuntu1
2020-07-22 13:23:15 upgrade evince:amd64 3.36.5-0ubuntu1 3.36.7-0ubuntu1
2020-07-22 13:23:17 upgrade libevdocument3-4:amd64 3.36.5-0ubuntu1 3.36.7-0ubuntu1
2020-07-22 13:23:18 upgrade libevview3-3:amd64 3.36.5-0ubuntu1 3.36.7-0ubuntu1
2020-07-22 13:23:19 upgrade libnss3:amd64 2:3.49.1-1ubuntu1.2 2:3.49.1-1ubuntu1.3
2020-07-22 13:23:20 upgrade evolution-data-server:amd64 3.36.3-0ubuntu1 3.36.4-0ubuntu1
2020-07-22 13:23:21 upgrade libcamel-1.2-62:amd64 3.36.3-0ubuntu1 3.36.4-0ubuntu1
2020-07-22 13:23:21 upgrade evolution-data-server-common:all 3.36.3-0ubuntu1 3.36.4-0ubuntu1
2020-07-22 13:23:22 upgrade libedataserver-1.2-24:amd64 3.36.3-0ubuntu1 3.36.4-0ubuntu1
2020-07-22 13:23:23 upgrade libecal-2.0-1:amd64 3.36.3-0ubuntu1 3.36.4-0ubuntu1
2020-07-22 13:23:24 upgrade libedata-cal-2.0-1:amd64 3.36.3-0ubuntu1 3.36.4-0ubuntu1
2020-07-22 13:23:25 upgrade libebook-contacts-1.2-3:amd64 3.36.3-0ubuntu1 3.36.4-0ubuntu1
2020-07-22 13:23:26 upgrade libedata-book-1.2-26:amd64 3.36.3-0ubuntu1 3.36.4-0ubuntu1
2020-07-22 13:23:26 upgrade libebackend-1.2-10:amd64 3.36.3-0ubuntu1 3.36.4-0ubuntu1
2020-07-22 13:23:27 upgrade libebook-1.2-20:amd64 3.36.3-0ubuntu1 3.36.4-0ubuntu1
2020-07-22 13:23:28 upgrade libedataserverui-1.2-2:amd64 3.36.3-0ubuntu1 3.36.4-0ubuntu1
2020-07-22 13:23:28 upgrade mutter-common:all 3.36.3-0ubuntu0.20.04.1 3.36.4-0ubuntu0.20.04.1
2020-07-22 13:23:29 upgrade gir1.2-mutter-6:amd64 3.36.3-0ubuntu0.20.04.1 3.36.4-0ubuntu0.20.04.1
2020-07-22 13:23:30 upgrade libmutter-6-0:amd64 3.36.3-0ubuntu0.20.04.1 3.36.4-0ubuntu0.20.04.1
2020-07-22 13:23:31 upgrade im-config:all 0.44-1ubuntu1 0.44-1ubuntu1.1
2020-07-22 13:23:32 upgrade libfprint-2-2:amd64 1:1.90.1+tod1-0ubuntu4 1:1.90.2+tod1-0ubuntu1~20.04.1
2020-07-22 13:23:33 upgrade libfprint-2-tod1:amd64 1:1.90.1+tod1-0ubuntu4 1:1.90.2+tod1-0ubuntu1~20.04.1
2020-07-22 13:23:34 upgrade linux-firmware:all 1.187.1 1.187.2
2020-07-22 13:23:45 upgrade simple-scan:amd64 3.36.0-0ubuntu1 3.36.3-0ubuntu0.20.04.0
2020-07-22 13:23:47 upgrade yaru-theme-gnome-shell:all 20.04.7 20.04.8
2020-07-22 13:23:48 upgrade yaru-theme-gtk:all 20.04.7 20.04.8
2020-07-22 13:23:49 upgrade yaru-theme-icon:all 20.04.7 20.04.8
2020-07-22 13:23:53 upgrade yaru-theme-sound:all 20.04.7 20.04.8
2020-07-22 13:23:54 upgrade mutter:amd64 3.36.3-0ubuntu0.20.04.1 3.36.4-0ubuntu0.20.04.1
2020-07-22 21:46:00 upgrade ffmpeg:amd64 7:4.2.2-1ubuntu1 7:4.2.4-1ubuntu0.1
2020-07-22 21:46:01 upgrade libavdevice58:amd64 7:4.2.2-1ubuntu1 7:4.2.4-1ubuntu0.1
2020-07-22 21:46:02 upgrade libavfilter7:amd64 7:4.2.2-1ubuntu1 7:4.2.4-1ubuntu0.1
2020-07-22 21:46:03 upgrade libswscale5:amd64 7:4.2.2-1ubuntu1 7:4.2.4-1ubuntu0.1
2020-07-22 21:46:03 upgrade libavformat58:amd64 7:4.2.2-1ubuntu1 7:4.2.4-1ubuntu0.1
2020-07-22 21:46:04 upgrade libavcodec58:amd64 7:4.2.2-1ubuntu1 7:4.2.4-1ubuntu0.1
2020-07-22 21:46:05 upgrade libswresample3:amd64 7:4.2.2-1ubuntu1 7:4.2.4-1ubuntu0.1
2020-07-22 21:46:06 upgrade libpostproc55:amd64 7:4.2.2-1ubuntu1 7:4.2.4-1ubuntu0.1
2020-07-22 21:46:07 upgrade libavresample4:amd64 7:4.2.2-1ubuntu1 7:4.2.4-1ubuntu0.1
2020-07-22 21:46:07 upgrade libavutil56:amd64 7:4.2.2-1ubuntu1 7:4.2.4-1ubuntu0.1
2020-07-22 21:46:09 upgrade libsnmp-base:all 5.8+dfsg-2ubuntu2.1 5.8+dfsg-2ubuntu2.2
2020-07-22 21:46:10 upgrade libsnmp35:amd64 5.8+dfsg-2ubuntu2.1 5.8+dfsg-2ubuntu2.2
2020-07-22 21:46:11 upgrade unattended-upgrades:all 2.3 2.3ubuntu0.1

Some help would be really appreciated. Thanks.
Also, please tell me if more info is needed (logs, etc.).

EDIT
After doing some research, and trying to reproduce the problem, I came across this in syslog:

Jul 23 11:23:40 razorback gnome-shell[6832]: **
Jul 23 11:23:40 razorback gnome-shell[6832]: mutter:ERROR:../src/backends/x11/meta-monitor-manager-xrandr.c:211:meta_monitor_manager_xrandr_update_screen_size: assertion failed: (width > 0 && height > 0 && scale > 0)
Jul 23 11:23:40 razorback gnome-shell[6832]: Bail out! mutter:ERROR:../src/backends/x11/meta-monitor-manager-xrandr.c:211:meta_monitor_manager_xrandr_update_screen_size: assertion failed: (width > 0 && height > 0 && scale > 0)
Jul 23 11:23:40 razorback gnome-shell[6832]: GNOME Shell crashed with signal 6
Jul 23 11:23:40 razorback gnome-shell[6832]: == Stack trace for context 0x5605f4678700 ==
Jul 23 11:23:42 razorback systemd[2371]: gnome-shell-x11.service: Main process exited, code=dumped, status=6/ABRT
Jul 23 11:23:42 razorback systemd[2371]: gnome-shell-x11.service: Failed with result 'core-dump'.
Jul 23 11:23:42 razorback systemd[2371]: gnome-shell-x11.service: Scheduled restart job, restart counter is at 1.
Jul 23 11:23:42 razorback systemd[2371]: Stopped target GNOME X11 Session (session: ubuntu).
Jul 23 11:23:42 razorback systemd[2371]: Stopping GNOME X11 Session (session: ubuntu).
Jul 23 11:23:42 razorback systemd[2371]: Stopped target GNOME X11 Session.
Jul 23 11:23:42 razorback systemd[2371]: Stopping GNOME X11 Session.
Jul 23 11:23:42 razorback systemd[2371]: Stopped target GNOME Shell on X11.
Jul 23 11:23:42 razorback systemd[2371]: Stopping GNOME Shell on X11.
Jul 23 11:23:42 razorback systemd[2371]: Stopped GNOME Shell on X11.
Jul 23 11:23:42 razorback systemd[2371]: Starting GNOME Shell on X11...
Jul 23 11:23:45 razorback /usr/lib/gdm3/gdm-x-session[6713]: (II) event5  - Logitech G403 Prodigy Gaming Mouse: SYN_DROPPED event - some input events have been lost.
Jul 23 11:23:46 razorback gnome-shell[21905]: **
Jul 23 11:23:46 razorback gnome-shell[21905]: mutter:ERROR:../src/backends/x11/meta-monitor-manager-xrandr.c:211:meta_monitor_manager_xrandr_update_screen_size: assertion failed: (width > 0 && height > 0 && scale > 0)
Jul 23 11:23:46 razorback gnome-shell[21905]: Bail out! mutter:ERROR:../src/backends/x11/meta-monitor-manager-xrandr.c:211:meta_monitor_manager_xrandr_update_screen_size: assertion failed: (width > 0 && height > 0 && scale > 0)
Jul 23 11:23:46 razorback systemd[2371]: gnome-shell-x11.service: Main process exited, code=dumped, status=6/ABRT
Jul 23 11:23:46 razorback systemd[2371]: gnome-shell-x11.service: Failed with result 'core-dump'.
Jul 23 11:23:46 razorback systemd[2371]: Failed to start GNOME Shell on X11.
Jul 23 11:23:46 razorback systemd[2371]: Dependency failed for GNOME Shell on X11.
Jul 23 11:23:46 razorback systemd[2371]: Dependency failed for GNOME X11 Session.
Jul 23 11:23:46 razorback systemd[2371]: Dependency failed for GNOME X11 Session (session: ubuntu).
Jul 23 11:23:46 razorback systemd[2371]: [email protected]: Job [email protected]/start failed with result 'dependency'.
Jul 23 11:23:46 razorback systemd[2371]: gnome-session-x11.target: Job gnome-session-x11.target/start failed with result 'dependency'.
Jul 23 11:23:46 razorback systemd[2371]: gnome-shell-x11.target: Job gnome-shell-x11.target/start failed with result 'dependency'.
Jul 23 11:23:46 razorback systemd[2371]: gnome-shell-x11.service: Scheduled restart job, restart counter is at 2.
Jul 23 11:23:46 razorback systemd[2371]: Stopped GNOME Shell on X11.
Jul 23 11:23:46 razorback systemd[2371]: Starting GNOME Shell on X11...
Jul 23 11:23:46 razorback gnome-shell[21946]: **
Jul 23 11:23:46 razorback gnome-shell[21946]: mutter:ERROR:../src/backends/x11/meta-monitor-manager-xrandr.c:211:meta_monitor_manager_xrandr_update_screen_size: assertion failed: (width > 0 && height > 0 && scale > 0)
Jul 23 11:23:46 razorback gnome-shell[21946]: Bail out! mutter:ERROR:../src/backends/x11/meta-monitor-manager-xrandr.c:211:meta_monitor_manager_xrandr_update_screen_size: assertion failed: (width > 0 && height > 0 && scale > 0)
Jul 23 11:23:46 razorback systemd[2371]: gnome-shell-x11.service: Main process exited, code=dumped, status=6/ABRT
Jul 23 11:23:46 razorback systemd[2371]: gnome-shell-x11.service: Failed with result 'core-dump'.
Jul 23 11:23:46 razorback systemd[2371]: Failed to start GNOME Shell on X11.
Jul 23 11:23:46 razorback systemd[2371]: gnome-shell-x11.service: Scheduled restart job, restart counter is at 3.
Jul 23 11:23:46 razorback systemd[2371]: Stopped GNOME Shell on X11.
Jul 23 11:23:46 razorback systemd[2371]: Starting GNOME Shell on X11...
Jul 23 11:23:46 razorback gnome-shell[21961]: **
Jul 23 11:23:46 razorback gnome-shell[21961]: mutter:ERROR:../src/backends/x11/meta-monitor-manager-xrandr.c:211:meta_monitor_manager_xrandr_update_screen_size: assertion failed: (width > 0 && height > 0 && scale > 0)
Jul 23 11:23:46 razorback gnome-shell[21961]: Bail out! mutter:ERROR:../src/backends/x11/meta-monitor-manager-xrandr.c:211:meta_monitor_manager_xrandr_update_screen_size: assertion failed: (width > 0 && height > 0 && scale > 0)
Jul 23 11:23:47 razorback systemd[2371]: gnome-shell-x11.service: Main process exited, code=dumped, status=6/ABRT
Jul 23 11:23:47 razorback systemd[2371]: gnome-shell-x11.service: Failed with result 'core-dump'.
Jul 23 11:23:47 razorback systemd[2371]: Failed to start GNOME Shell on X11.
Jul 23 11:23:47 razorback systemd[2371]: gnome-shell-x11.service: Scheduled restart job, restart counter is at 4.
Jul 23 11:23:47 razorback systemd[2371]: Stopped GNOME Shell on X11.
Jul 23 11:23:47 razorback systemd[2371]: gnome-shell-x11.service: Start request repeated too quickly.
Jul 23 11:23:47 razorback systemd[2371]: gnome-shell-x11.service: Failed with result 'core-dump'.
Jul 23 11:23:47 razorback systemd[2371]: Failed to start GNOME Shell on X11.
Jul 23 11:23:47 razorback systemd[2371]: gnome-shell-x11.service: Triggering OnFailure= dependencies.
Jul 23 11:23:47 razorback systemd[2371]: Started GNOME Session Failed lockdown screen (user).
Jul 23 11:23:47 razorback systemd[2371]: Reached target GNOME Session Failed.
Jul 23 11:23:47 razorback systemd[2371]: Condition check resulted in Disable GNOME Shell extensions after failure being skipped.

After that, I could start session normally.

EDIT
Tried switching to Wayland and the problem is gone. So the issue is with X11.