I have tried this in Autocad 2010-2013 when I set MENUBAR=1 and open 2 or more drawings. I see the max/restore/close icons in te top right of the menubar. As I minimize both drawings and then restore 1 to maximize, the icons at then top right of the menubar disappear.
I have then got to either use the Window menubar option to select the other drawing to make the icons re-appear.
I could then use the Quickviewdrawings icon at the bottom to make the icon reappear.
Is this still a bug as i have tested this in acad 2013.