There is a funny bug when one tries to display a sub-menu from multi-column menu: if the sub-menu is displayed over the parent menu (and not next to it, since the parent menu has two columns), when I mouse the mouse over the submenu, it disappears. It is related to mouse movements since keyboard navigation works fine. It is easy to reproduce that issue in the juce demo: in WidgetsDemo.cpp line 1244, add:
for (int i=0; i < 100; ++i) m.addItem(300+i, "BALAI_BROSSE" + String(i));
Then you’ll have a two-columns menu and the bug is easy to spot. It does not appear on windows.