Wrong selected file in XDG portals save diaiog

I experienced a bug when running my program in the flatpak environment. Before I open a save dialog from QtQuick.Dialogs, I initialize the file name by setting the selectedFile property. But when I open the dialog a second time with a different value for selectedFile, it still shows the file of the first time as the selected file.

This only happens in the flatpak environment, the same program works fine when QtQuick.Dialogs uses a native file dialog, so I assume that there is a bug in Qt's xdgdesktopportal plugin.