Created attachment 168725 [details]
Picture of small popup.

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SUMMARY
When I click any icon(arrow, wifi, sound, etc), popup shows up. But it is way too small. About 5 pixels width and height.

STEPS TO REPRODUCE
1. Add System tray to panel.
2. Click any of icon.

OBSERVED RESULT
Very very small popup shows up.

EXPECTED RESULT
Normal sized popup, obviously.

SOFTWARE/OS VERSIONS
Windows: No
macOS: No
Linux Kernel Version:  6.8.7-arch1-1(64-bit)
(available in About System)
KDE Plasma Version: 6.0.4
KDE Frameworks Version: 6.1.0
Qt Version: 6.7.0

ADDITIONAL INFORMATION
There is suspicious log I think at beginning when plasmashell was executed.

file:///usr/share/plasma/plasmoids/org.kde.plasma.private.systemtray/contents/ui/main.qml:162:21: QML KSortFilterProxyModel: Binding loop detected for property "sourceModel"
file:///usr/share/plasma/plasmoids/org.kde.plasma.private.systemtray/contents/ui/main.qml:162:21: QML KSortFilterProxyModel: Binding loop detected for property "sourceModel"
qml: SystemTray ItemLoader: Invalid state, cannot determine source!

I know nothing about QML, But I think this would help investigating the problem.