I'm seeing something slightly different to what you're describing in a xenial VM: submenus do open empty indeed, however after a fraction of a second they are redrawn with the correct menu entries.
Can you confirm that in your case you need to close the menu and re-open it again to make its content appear?
I'm seeing something slightly different to what you're describing in a xenial VM: submenus do open empty indeed, however after a fraction of a second they are redrawn with the correct menu entries.
Can you confirm that in your case you need to close the menu and re-open it again to make its content appear?