SUMMARY
KDE global menu placed on Latte Dock don't go away on closing Systemsettings. Other apps don't have such an issue.

STEPS TO REPRODUCE
1. Create Latte Dock panel and place KDE global menu widget on it.
2. Create regular KDE panel with KDE global menu widget on it.
3. Run KDE Systemsettings.
4. Switch to any app that doesn't expose own app menu to the global menu widget (global meny is empty).
5. Switch to KDE System settings and close it in any way.

OBSERVED RESULT
The focus returns to the app from step 4 above. KDE Systemsettings app menu disappears from the regular KDE panel, but keeps being present on the Latte Dock panel. Clicking menu's items gives no result. The menu goes away on switching to another app which exposes its menu to the global menu widget.

EXPECTED RESULT
KDE Systemsettings app menu goes away from both panels on app's closing.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: KDE neon 5.23 (based on Ubuntu 20.04)
KDE Plasma Version: 5.23.2
KDE Frameworks Version: 5.87.1
Qt Version: 5.15.3

ADDITIONAL INFORMATION
It may be an issue on the Latte Dock side, but may be not. KDE Systemsettings is the only app that demonstrates such an issue.