Created attachment 105199 [details] global menu bug It calls a menu and ignores selection, just calls the same menu again
Global menu is launching in different style by keyboard shortcut - then after clicking on any launched menu section or on global menu panel button - menu in different styling appears on top of previously launched by keyboard menu
Created attachment 110204 [details] differently-styled-global-menus
Additional observation: when this happens, the menu is not navigable by keyboard.
*** Bug 418574 has been marked as a duplicate of this bug. ***
Can confirm, shortcut invocation is broken for single button mode. Sometimes it opens something that looks like a tooltip with a single useless button "Global Menu", other times it opens the actual menu as well. However, this is exclusive to a shortcut: Using panel navigation via Meta+Alt+P and activating (e.g. pressing Space or Enter) does the same thing. And, yes, the keyboard navigation is naturally broken is such state, because keyboard focus goes to the weird popup.
*** Bug 378771 has been marked as a duplicate of this bug. ***
*** Bug 441990 has been marked as a duplicate of this bug. ***
Adding Fushan Wen to CC list, because accessibility concerns (including keyboard navigation) are his area of work.