Sleep (s2idle) Unresponsive After Plugging in USB3 Monitor

[skyfishgoo]

the reason i suggest the different states is because they might not all be comparable with your hardware, so finding one that works properly it the goal (that includes waking up properly as well)... you would have to examine you journal logs so see if there is any difference between calling systemctl vs, just writing to those files.

i know for instance you need to write to both mem_sleep and state to get certain results and if you don't do the in the correct order the results may be confusing... which is why i let systemctl do it.

do you have a firmware setting about usb power and wake on usb device ... if so turn that on and the USB ports will remain active and powered while in suspend or hibernate.

[hexintor]

I'm aware # has to be removed to uncomment the config line. According to the docs the commented lines reflect the default, so for the case of AllowSuspend it doesn't make sense to uncomment it just to leave it the same as the default. Regardless I did uncomment AllowSuspend and modified the others as suggested:

AllowSuspend=yes
SuspendState=freeze mem
MemorySleepMode=s2idle

Unfortunately it made no difference after running systemctl suspend. So I think we can rule out systemd making a difference.

I also tried kernel param acpi_sleep=s4_nohwsig via /etc/default/grub:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_sleep=s4_nohwsig"

grub-update output:

Sourcing file `/etc/default/grub'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-6.11.0-14-generic
Found initrd image: /boot/initrd.img-6.11.0-14-generic
Found linux image: /boot/vmlinuz-6.11.0-13-generic
Found initrd image: /boot/initrd.img-6.11.0-13-generic
Found memtest86+ 64bit EFI image: /boot/memtest86+x64.efi
Warning: os-prober will be executed to detect other bootable partitions.
Its output will be used to detect bootable binaries on them and create new boot entries.
Found Windows Boot Manager on /dev/nvme0n1p1@/EFI/Microsoft/Boot/bootmgfw.efi
Adding boot menu entry for UEFI Firmware Settings ...
done

Same problems with both s2idle and S3 after a restart.

For reference here is comparison of journalctl output of s2idle resuming correctly overnight from closing the laptop lid and opening it this morning, and then a journalctl of a s2idle resuming failure (plugging in USB3 monitor while asleep)

journalctl output of s2idle resuming correctly opening laptop lid at Feb 10 11:10:48 and looks like sleep state was reached at Feb 09 23:50:43:

Feb 09 23:50:43 systemd-logind[710]: The system will suspend now!
Feb 09 23:50:43 ModemManager[804]: <msg> [sleep-monitor-systemd] system is about to suspend
Feb 09 23:50:43 NetworkManager[747]: <info> [1739166643.3656] manager: sleep: sleep requested (sleeping: no enabled: yes)
Feb 09 23:50:43 NetworkManager[747]: <info> [1739166643.3659] device (p2p-dev-wlp0s20f3): state change: disconnected -> unmanaged (reason 'unmanaged-sleeping', sys-iface-state: 'managed')
Feb 09 23:50:43 NetworkManager[747]: <info> [1739166643.3667] manager: NetworkManager state is now ASLEEP
Feb 09 23:50:43 NetworkManager[747]: <info> [1739166643.3669] device (wlp0s20f3): state change: activated -> deactivating (reason 'sleeping', sys-iface-state: 'managed')
Feb 09 23:50:43 NetworkManager[747]: <info> [1739166643.3670] dhcp4 (wlp0s20f3): canceled DHCP transaction
Feb 09 23:50:43 NetworkManager[747]: <info> [1739166643.3671] dhcp4 (wlp0s20f3): activation: beginning transaction (timeout in 45 seconds)
Feb 09 23:50:43 NetworkManager[747]: <info> [1739166643.3671] dhcp4 (wlp0s20f3): state changed no lease
Feb 09 23:50:43 google-chrome-stable[2538]: [2533:2560:0209/235043.368511:ERROR:connection_factory_impl.cc(483 )] ConnectionHandler failed with net error: -2
Feb 09 23:50:43 google-chrome-stable[2538]: [2533:2560:0209/235043.371778:ERROR:connection_factory_impl.cc(434 )] Failed to connect to MCS endpoint with error -105
Feb 09 23:50:43 systemd-resolved[622]: wlp0s20f3: Bus client reset search domain list.
Feb 09 23:50:43 kded6[2000]: Service ":1.91" unregistered
Feb 09 23:50:43 kded6[2000]: org.kde.plasma.nm.kded: Unhandled active connection state change: 3
Feb 09 23:50:43 avahi-daemon[685]: Withdrawing address record for 192.168.29.108 on wlp0s20f3.
Feb 09 23:50:43 systemd-resolved[622]: wlp0s20f3: Bus client set default route setting: no
Feb 09 23:50:43 avahi-daemon[685]: Leaving mDNS multicast group on interface wlp0s20f3.IPv4 with address 192.168.29.108.
Feb 09 23:50:43 systemd-resolved[622]: wlp0s20f3: Bus client reset DNS server list.
Feb 09 23:50:43 avahi-daemon[685]: Interface wlp0s20f3.IPv4 no longer relevant for mDNS.
Feb 09 23:50:43 systemd[1]: Starting NetworkManager-dispatcher.service - Network Manager Script Dispatcher Service...
Feb 09 23:50:43 avahi-daemon[685]: Withdrawing address record for fe80::2aca:605a:7e4a:c5b3 on wlp0s20f3.
Feb 09 23:50:43 avahi-daemon[685]: Leaving mDNS multicast group on interface wlp0s20f3.IPv6 with address fe80::2aca:605a:7e4a:c5b3.
Feb 09 23:50:43 avahi-daemon[685]: Interface wlp0s20f3.IPv6 no longer relevant for mDNS.
Feb 09 23:50:43 dbus-daemon[688]: [system] Activating via systemd: service name='org.freedesktop.nm_dispatcher' unit='dbus-org.freedesktop.nm-dispatcher.service' requested by ':1.11' (uid=0 pid=747 comm=
"/usr/sbin/NetworkManager --no-daemon" label="unconfined")
Feb 09 23:50:43 dbus-daemon[688]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
Feb 09 23:50:43 systemd[1]: Started NetworkManager-dispatcher.service - Network Manager Script Dispatcher Service.
Feb 09 23:50:43 kernel: wlp0s20f3: deauthenticating from 08:62:66:cb:2c:24 by local choice (Reason: 3=DEAUTH_LEAVING)
Feb 09 23:50:43 wpa_supplicant[750]: wlp0s20f3: CTRL-EVENT-DISCONNECTED bssid=08:62:66:cb:2c:24 reason=3 locally_generated=1
Feb 09 23:50:43 wpa_supplicant[750]: wlp0s20f3: CTRL-EVENT-DSCP-POLICY clear_all
Feb 09 23:50:43 NetworkManager[747]: <info> [1739166643.4659] device (wlp0s20f3): state change: deactivating -> disconnected (reason 'sleeping', sys-iface-state: 'managed')
Feb 09 23:50:43 NetworkManager[747]: <info> [1739166643.4679] device (wlp0s20f3): supplicant interface state: completed -> disconnected
Feb 09 23:50:43 NetworkManager[747]: <info> [1739166643.4680] device (wlp0s20f3): state change: disconnected -> unmanaged (reason 'unmanaged-sleeping', sys-iface-state: 'managed')
Feb 09 23:50:43 wpa_supplicant[750]: p2p-dev-wlp0s20: CTRL-EVENT-DSCP-POLICY clear_all
Feb 09 23:50:43 wpa_supplicant[750]: p2p-dev-wlp0s20: CTRL-EVENT-DSCP-POLICY clear_all
Feb 09 23:50:43 wpa_supplicant[750]: nl80211: deinit ifname=p2p-dev-wlp0s20 disabled_11b_rates=0
Feb 09 23:50:43 systemd[1]: Reached target sleep.target - Sleep.
Feb 09 23:50:43 systemd[1]: Starting systemd-suspend.service - System Suspend...
Feb 09 23:50:43 wpa_supplicant[750]: wlp0s20f3: CTRL-EVENT-DSCP-POLICY clear_all
Feb 09 23:50:43 systemd-sleep[26208]: Successfully froze unit 'user.slice'.
Feb 09 23:50:43 systemd-sleep[26208]: Performing sleep operation 'suspend'...
Feb 09 23:50:43 kernel: PM: suspend entry (s2idle)
Feb 09 23:50:43 kernel: Filesystems sync: 0.002 seconds
Feb 09 23:50:43 wpa_supplicant[750]: wlp0s20f3: CTRL-EVENT-DSCP-POLICY clear_all
Feb 09 23:50:43 wpa_supplicant[750]: nl80211: deinit ifname=wlp0s20f3 disabled_11b_rates=0
Feb 10 11:10:48 kernel: Freezing user space processes
Feb 10 11:10:48 kernel: Freezing user space processes completed (elapsed 0.002 seconds)
Feb 10 11:10:48 kernel: OOM killer disabled.
Feb 10 11:10:48 kernel: Freezing remaining freezable tasks
Feb 10 11:10:48 kernel: Freezing remaining freezable tasks completed (elapsed 0.001 seconds)
Feb 10 11:10:48 kernel: printk: Suspending console(s) (use no_console_suspend to debug)
Feb 10 11:10:48 kernel: ACPI: EC: interrupt blocked
Feb 10 11:10:48 kernel: ACPI: EC: interrupt unblocked
Feb 10 11:10:48 kernel: OOM killer enabled.
Feb 10 11:10:48 kernel: Restarting tasks ...
Feb 10 11:10:48 kernel: mei_hdcp 0000:00:16.0-b638ab7e-94e2-4ea2-a552-d1c54b627f04: bound 0000:00:02.0 (ops i915_hdcp_ops [i915])
Feb 10 11:10:48 kernel: done.
Feb 10 11:10:48 kernel: random: crng reseeded on system resumption
Feb 10 11:10:48 systemd-resolved[622]: Clock change detected. Flushing caches.
Feb 10 11:10:48 systemd-logind[710]: Lid closed.
Feb 10 11:10:48 kernel: mei_pxp 0000:00:16.0-fbf6fcf1-96cf-4e2e-a6a6-1bab8cbe36b1: bound 0000:00:02.0 (ops i915_pxp_tee_component_ops [i915])
Feb 10 11:10:48 systemd-logind[710]: Lid opened.
Feb 10 11:10:48 systemd-sleep[26208]: System returned from sleep operation 'suspend'.
Feb 10 11:10:48 kernel: PM: suspend exit
Feb 10 11:10:48 bluetoothd[686]: Controller resume with wake event 0x0
Feb 10 11:10:48 systemd[1]: anacron.service - Run anacron jobs was skipped because of an unmet condition check (ConditionACPower=true).
Feb 10 11:10:48 systemd[1]: apt-daily.service - Daily apt download activities was skipped because of an unmet condition check (ConditionACPower=true).
Feb 10 11:10:48 systemd[1]: apt-daily-upgrade.service - Daily apt upgrade and clean activities was skipped because of an unmet condition check (ConditionACPower=true).
Feb 10 11:10:48 systemd[1]: Starting dpkg-db-backup.service - Daily dpkg database backup service...
Feb 10 11:10:48 systemd[1]: Starting fstrim.service - Discard unused blocks on filesystems from /etc/fstab...
Feb 10 11:10:48 systemd[1]: Starting fwupd-refresh.service - Refresh fwupd metadata and update motd...
Feb 10 11:10:48 systemd[1]: Starting motd-news.service - Message of the Day...
Feb 10 11:10:48 systemd[1]: plocate-updatedb.service - Update the plocate database was skipped because of an unmet condition check (ConditionACPower=true).
Feb 10 11:10:48 systemd[1]: Starting sysstat-collect.service - system activity accounting tool...
Feb 10 11:10:48 systemd[1]: Starting sysstat-rotate.service - system activity accounting tool...
Feb 10 11:10:48 systemd[1]: Starting sysstat-summary.service - Generate a daily summary of process accounting...
Feb 10 11:10:48 systemd[1]: logrotate.service - Rotate log files was skipped because of an unmet condition check (ConditionACPower=true).
Feb 10 11:10:48 systemd[1]: man-db.service - Daily man-db regeneration was skipped because of an unmet condition check (ConditionACPower=true).
Feb 10 11:10:48 systemd[1]: motd-news.service: Deactivated successfully.
Feb 10 11:10:48 systemd[1]: Finished motd-news.service - Message of the Day.
Feb 10 11:10:48 systemd-sleep[26208]: Successfully thawed unit 'user.slice'.
Feb 10 11:10:48 systemd[1]: systemd-suspend.service: Deactivated successfully.
Feb 10 11:10:48 systemd[1]: Finished systemd-suspend.service - System Suspend.
Feb 10 11:10:48 systemd[1]: sysstat-collect.service: Deactivated successfully.
Feb 10 11:10:48 systemd[1]: Finished sysstat-collect.service - system activity accounting tool.
Feb 10 11:10:48 systemd[1]: Stopped target sleep.target - Sleep.
Feb 10 11:10:48 systemd[1]: Reached target suspend.target - Suspend.
Feb 10 11:10:48 systemd-logind[710]: Operation 'suspend' finished.
Feb 10 11:10:48 systemd[1]: Starting grub-common.service - Record successful boot for GRUB...
Feb 10 11:10:48 systemd[1]: sysstat-rotate.service: Deactivated successfully.
Feb 10 11:10:48 systemd[1]: Finished sysstat-rotate.service - system activity accounting tool.
Feb 10 11:10:48 systemd-resolved[622]: Closing all remaining TCP connections.
Feb 10 11:10:48 systemd-resolved[622]: Resetting learnt feature levels on all servers.
Feb 10 11:10:48 ModemManager[804]: <msg> [sleep-monitor-systemd] system is resuming
Feb 10 11:10:48 systemd[1]: Stopped target suspend.target - Suspend.
Feb 10 11:10:48 NetworkManager[747]: <info> [1739207448.7506] manager: sleep: wake requested (sleeping: yes enabled: yes)
Feb 10 11:10:48 NetworkManager[747]: <info> [1739207448.7507] device (wlp0s20f3): state change: unmanaged -> unavailable (reason 'managed', sys-iface-state: 'external')
Feb 10 11:10:48 systemd[1]: grub-common.service: Deactivated successfully.
Feb 10 11:10:48 systemd[1]: Finished grub-common.service - Record successful boot for GRUB.
Feb 10 11:10:48 systemd[1]: Starting grub-initrd-fallback.service - GRUB failed boot detection...
Feb 10 11:10:48 systemd[1]: sysstat-summary.service: Deactivated successfully.
Feb 10 11:10:48 systemd[1]: Finished sysstat-summary.service - Generate a daily summary of process accounting.
Feb 10 11:10:48 dbus-daemon[688]: [system] Activating service name='org.kde.powerdevil.backlighthelper' requested by ':1.73' (uid=1000 pid=2119 comm="/usr/lib/x86_64-linux-gnu/libexec/org_kde_powerdev" l
abel="unconfined") (using servicehelper)
Feb 10 11:10:48 org.kde.powerdevil.backlighthelper[26425]: Detected locale "C" with character encoding "ANSI_X3.4-1968", which is not UTF-8.
Qt depends on a UTF-8 locale, and has switched to "C.UTF-8" instead.
If this causes problems, reconfigure your locale. See the locale(1) manual
for more information.
Feb 10 11:10:48 systemd[1]: grub-initrd-fallback.service: Deactivated successfully.
Feb 10 11:10:48 systemd[1]: Finished grub-initrd-fallback.service - GRUB failed boot detection.
Feb 10 11:10:48 dbus-daemon[688]: [system] Successfully activated service 'org.kde.powerdevil.backlighthelper'
Feb 10 11:10:48 systemd[1]: dpkg-db-backup.service: Deactivated successfully.
Feb 10 11:10:48 systemd[1]: Finished dpkg-db-backup.service - Daily dpkg database backup service.
Feb 10 11:10:48 NetworkManager[747]: <info> [1739207448.9501] device (p2p-dev-wlp0s20f3): state change: unmanaged -> unavailable (reason 'managed', sys-iface-state: 'external')
Feb 10 11:10:48 NetworkManager[747]: <info> [1739207448.9503] manager: NetworkManager state is now CONNECTED_LOCAL
Feb 10 11:10:48 NetworkManager[747]: <info> [1739207448.9722] device (wlp0s20f3): supplicant interface state: internal-starting -> disconnected
Feb 10 11:10:48 NetworkManager[747]: <info> [1739207448.9722] device (p2p-dev-wlp0s20f3): state change: unavailable -> unmanaged (reason 'unmanaged-link-not-init', sys-iface-state: 'removed')
Feb 10 11:10:48 NetworkManager[747]: <info> [1739207448.9727] Wi-Fi P2P device controlled by interface wlp0s20f3 created
Feb 10 11:10:48 NetworkManager[747]: <info> [1739207448.9729] manager: (p2p-dev-wlp0s20f3): new 802.11 Wi-Fi P2P device (/org/freedesktop/NetworkManager/Devices/8)
Feb 10 11:10:48 NetworkManager[747]: <info> [1739207448.9732] device (p2p-dev-wlp0s20f3): state change: unmanaged -> unavailable (reason 'managed', sys-iface-state: 'external')
Feb 10 11:10:48 NetworkManager[747]: <info> [1739207448.9737] device (wlp0s20f3): state change: unavailable -> disconnected (reason 'supplicant-available', sys-iface-state: 'managed')
Feb 10 11:10:48 NetworkManager[747]: <info> [1739207448.9742] device (p2p-dev-wlp0s20f3): state change: unavailable -> disconnected (reason 'none', sys-iface-state: 'managed')
Feb 10 11:10:48 fwupdmgr[26295]: Updating lvfs

Unsuccessful/crash s2idle resuming after plugging in USB3 Monitor:

Feb 10 11:16:30 systemd-logind[710]: The system will suspend now!
Feb 10 11:16:30 ModemManager[804]: <msg> [sleep-monitor-systemd] system is about to suspend
Feb 10 11:16:30 NetworkManager[747]: <info> [1739207790.4635] manager: sleep: sleep requested (sleeping: no enabled: yes)
Feb 10 11:16:30 NetworkManager[747]: <info> [1739207790.4637] device (p2p-dev-wlp0s20f3): state change: disconnected -> unmanaged (reason 'unmanaged-sleeping', sys-iface-state: 'managed')
Feb 10 11:16:30 NetworkManager[747]: <info> [1739207790.4649] manager: NetworkManager state is now ASLEEP
Feb 10 11:16:30 NetworkManager[747]: <info> [1739207790.4651] device (wlp0s20f3): state change: activated -> deactivating (reason 'sleeping', sys-iface-state: 'managed')
Feb 10 11:16:30 NetworkManager[747]: <info> [1739207790.4652] dhcp4 (wlp0s20f3): canceled DHCP transaction
Feb 10 11:16:30 NetworkManager[747]: <info> [1739207790.4652] dhcp4 (wlp0s20f3): activation: beginning transaction (timeout in 45 seconds)
Feb 10 11:16:30 NetworkManager[747]: <info> [1739207790.4652] dhcp4 (wlp0s20f3): state changed no lease
Feb 10 11:16:30 sudo[26784]: pam_unix(sudo:session): session closed for user root
Feb 10 11:16:30 google-chrome-stable[2538]: [2533:2560:0210/111630.466386:ERROR:connection_factory_impl.cc(483 )] ConnectionHandler failed with net error: -2
Feb 10 11:16:30 avahi-daemon[685]: Withdrawing address record for 192.168.29.108 on wlp0s20f3.
Feb 10 11:16:30 avahi-daemon[685]: Leaving mDNS multicast group on interface wlp0s20f3.IPv4 with address 192.168.29.108.
Feb 10 11:16:30 kded6[2000]: Service ":1.250" unregistered
Feb 10 11:16:30 avahi-daemon[685]: Interface wlp0s20f3.IPv4 no longer relevant for mDNS.
Feb 10 11:16:30 avahi-daemon[685]: Withdrawing address record for fe80::2aca:605a:7e4a:c5b3 on wlp0s20f3.
Feb 10 11:16:30 avahi-daemon[685]: Leaving mDNS multicast group on interface wlp0s20f3.IPv6 with address fe80::2aca:605a:7e4a:c5b3.
Feb 10 11:16:30 avahi-daemon[685]: Interface wlp0s20f3.IPv6 no longer relevant for mDNS.
Feb 10 11:16:30 kded6[2000]: org.kde.plasma.nm.kded: Unhandled active connection state change: 3
Feb 10 11:16:30 google-chrome-stable[2538]: [2533:2560:0210/111630.478981:ERROR:connection_factory_impl.cc(434 )] Failed to connect to MCS endpoint with error -105
Feb 10 11:16:30 dbus-daemon[688]: [system] Activating via systemd: service name='org.freedesktop.nm_dispatcher' unit='dbus-org.freedesktop.nm-dispatcher.service' requested by ':1.11' (uid=0 pid=747 comm=
"/usr/sbin/NetworkManager --no-daemon" label="unconfined")
Feb 10 11:16:30 systemd[1]: Starting NetworkManager-dispatcher.service - Network Manager Script Dispatcher Service...
Feb 10 11:16:30 systemd-resolved[622]: wlp0s20f3: Bus client reset search domain list.
Feb 10 11:16:30 systemd-resolved[622]: wlp0s20f3: Bus client set default route setting: no
Feb 10 11:16:30 systemd-resolved[622]: wlp0s20f3: Bus client reset DNS server list.
Feb 10 11:16:30 dbus-daemon[688]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
Feb 10 11:16:30 systemd[1]: Started NetworkManager-dispatcher.service - Network Manager Script Dispatcher Service.
Feb 10 11:16:30 kernel: wlp0s20f3: deauthenticating from 08:62:66:cb:2c:24 by local choice (Reason: 3=DEAUTH_LEAVING)
Feb 10 11:16:30 wpa_supplicant[750]: wlp0s20f3: CTRL-EVENT-DISCONNECTED bssid=08:62:66:cb:2c:24 reason=3 locally_generated=1
Feb 10 11:16:30 wpa_supplicant[750]: wlp0s20f3: CTRL-EVENT-DSCP-POLICY clear_all
Feb 10 11:16:30 NetworkManager[747]: <info> [1739207790.5864] device (wlp0s20f3): state change: deactivating -> disconnected (reason 'sleeping', sys-iface-state: 'managed')
Feb 10 11:16:30 NetworkManager[747]: <info> [1739207790.5900] device (wlp0s20f3): supplicant interface state: completed -> disconnected
Feb 10 11:16:30 NetworkManager[747]: <info> [1739207790.5902] device (wlp0s20f3): state change: disconnected -> unmanaged (reason 'unmanaged-sleeping', sys-iface-state: 'managed')
Feb 10 11:16:30 wpa_supplicant[750]: p2p-dev-wlp0s20: CTRL-EVENT-DSCP-POLICY clear_all
Feb 10 11:16:30 wpa_supplicant[750]: p2p-dev-wlp0s20: CTRL-EVENT-DSCP-POLICY clear_all
Feb 10 11:16:30 wpa_supplicant[750]: nl80211: deinit ifname=p2p-dev-wlp0s20 disabled_11b_rates=0
Feb 10 11:16:30 wpa_supplicant[750]: wlp0s20f3: CTRL-EVENT-DSCP-POLICY clear_all
Feb 10 11:16:30 wpa_supplicant[750]: wlp0s20f3: CTRL-EVENT-DSCP-POLICY clear_all
Feb 10 11:16:30 wpa_supplicant[750]: nl80211: deinit ifname=wlp0s20f3 disabled_11b_rates=0
Feb 10 11:16:30 kwin_wayland_wrapper[26787]: qml: The backend got an unknown wallpaper provider type. The wallpaper will now fall back to the default. Please check your wallpaper configuration!
Feb 10 11:16:31 systemd[1]: Reached target sleep.target - Sleep.
Feb 10 11:16:31 systemd[1]: Starting systemd-suspend.service - System Suspend...
Feb 10 11:16:31 systemd-sleep[26846]: Successfully froze unit 'user.slice'.
Feb 10 11:16:31 systemd-sleep[26846]: Performing sleep operation 'suspend'...
Feb 10 11:16:31 kernel: PM: suspend entry (s2idle)

[skyfishgoo]

try changing the kernel param from a 4 to a 2

unfortunately the logs don't show anything about why it didn't wake up, just like in my case, the logs only "log" up until it goes to sleep and the next log just starts from the reboot.

i still recommend using the systemctl command, and i don't understand your aversion to it... using the system tools as they were designed means just one less thing that could be introducing a variable as you try to troubleshoot.

i also recommend fully utilizing the sleep.config as your control method regardless what defaults may or may not be in place... again, it reduces the variables.

[hexintor]

I really thought we were onto something here!

Per your suggestion after modifying to GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_sleep=s2_nohwsig"

I successfully resumed from USB3 monitor connection while in s2idle sleep THREE times. In between each sequence I did a quick normal sleep/resume procedure without removing and reconnecting USB. For the FOURTH attempt I tried to do back-to-back sleep - connect USB3 Monitor while in sleep state - resume cycles and the second consecutive attempt failed to resume as described originally (keyboard unresponsive, PWR LED slow blinking, black laptop screen).

I'm no expert in these things. But it smells like a race condition considering the inconsistent behavior.