It seems that indicator-appmenu is loosing the window. For me this takes about 20 times of minimizing, but I have been able to reproduce it. When I call dbusmenu-dumper I get this:
$ /usr/lib/libdbusmenu/dbusmenu-dumper
** (dbusmenu-dumper:7660): WARNING **: Unable to call 'GetMenuForWindow' on registrar: GDBus.Error:com.canonical.AppMenu.Error: Window not found
ERROR: could not find a menu for the pointed window
It seems that indicator-appmenu is loosing the window. For me this takes about 20 times of minimizing, but I have been able to reproduce it. When I call dbusmenu-dumper I get this:
$ /usr/lib/ libdbusmenu/ dbusmenu- dumper
** (dbusmenu- dumper: 7660): WARNING **: Unable to call 'GetMenuForWindow' on registrar: GDBus.Error: com.canonical. AppMenu. Error: Window not found
ERROR: could not find a menu for the pointed window