This is related to #QTBUG-1894, which is not fixed completely in 4.8.4. It still exists while re-sizing. It is fixed for the scenario while moving the window by pressing on title bar. But if window is re-sized using corner re-sizable areas or while switching between maximize/normal window by clicking on '+' button on title bar, the pop-up menu still remains at the same position where it was popped up.