Tab Groups menu closing after "Move to Group" despite "Keep menu open"

[MartinPC]

I've activated the "Keep menu open" option in TabGroups Menu 0.9.1 in Firefox 19.0.2 on Windows 7. The "Tab Groups" menu (on the Menu Bar) stays open after I delete a tab in the "Tab Groups" menu tree, but not when I move one to a different group. This radically reduces the extension's usefulness as a tab organization tool.