On Windows, exiting the application normally (e.g., via the systray "Quit" menu action) can cause the application icon to persist in the system tray longer after the process has terminated -- probably due to the qt5reactor event loop stopping while Qt events still need to be processed. In any case, it would be preferable for this to not happen; Gridsync should explicitly call a hide() on the QSystemTrayIcon before the shutdown process begins to ensure that the icon doesn't linger.