SUMMARY
Whenever there's a brief power outage or the power cable of an external monitor is suddenly disconnected and later reconnected, Plasmashell does not restore the contents of that monitor; it acts as though it's a new desktop or something that uses default settings.

I have a laptop monitor on the left and an external monitor on the right.
On the external monitor, I have a custom wallpaper, a panel  with pinned apps, and the layout is set as Desktop instead of Folder view.
After a blackout or power cable disconnect and reconnect, the external monitor shows the default wallpaper (Milky Way), no panel, and a Folder view layout.

This only happens on the Wayland session, not the X11 one.

STEPS TO REPRODUCE
1. Customize your external monitor somewhat
2. Remove the power cable from the socket
3. Reconnect the power cable to the socket

OBSERVED RESULT
No retention/memory/reload of the previously set desktop.

EXPECTED RESULT
The desktop is reloaded just fine.

SOFTWARE/OS VERSIONS
Operating System: openSUSE Tumbleweed 20210427 (up-to-date Krypton despite the date)
KDE Plasma Version: 5.21.80
KDE Frameworks Version: 5.82.0
Qt Version: 5.15.2
Kernel Version: 5.12.0-1-default (64-bit)
Graphics Platform: Wayland
Processors: 4 × Intel® Core™ i5-7200U CPU @ 2.50GHz
Memory: 15.5 GiB of RAM
Graphics Processor: Mesa DRI Intel® HD Graphics 620

ADDITIONAL INFORMATION
Restarting Plasmashell fixes the issue.
I am not using systemd startup.
I've been experiencing this issue for a while now.

The following shows up when running journalctl -f /usr/bin/plasmashell

After disconnect:
file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Desktop.qml:146:19: QML Loader: Binding loop detected for property "height"
file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Panel.qml:97: TypeError: Cannot read property 'enabledBorders' of null
file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Panel.qml:78: TypeError: Cannot read property 'screenGeometry' of null
file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Panel.qml:161: TypeError: Cannot read property 'opacityMode' of null
file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Desktop.qml:121: TypeError: Cannot read property 'x' of null
file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Desktop.qml:135: TypeError: Cannot read property 'y' of null
file:///usr/share/plasma/shells/org.kde.plasma.desktop/contents/views/Panel.qml:26:1: QML Panel: Binding loop detected for property "state"
trying to show an empty dialog

After reconnect:
requesting unexisting screen 1