Using Wayland backend and gtk3 SAL plugin, gnome-shell 3.20 and "mouse" or "sloppy" focus mode, all the menus in the interface (main menu, style, font selection...) just disappears when moving the mouse inside the menu.
Occurs : always
Steps to reproduice :
run gnome-shell wayland session
run libreoffice with SAL_USE_VCLPLUGIN=gtk3, GDK_BACKEND='wayland'
set via gsettings focus mode to "mouse" or "sloppy" : org.gnome.desktop.wm.preferences focus-mode 'sloppy'
try to use menus, moving the mouse on it.
If you use another gtk3 application that has a menubar, e.g. glade, does it do the same thing ?
I strongly suspect that this is https://bugzilla.gnome.org/show_bug.cgi?id=768016