Sub-menu indicator not working correctly in menus

Getting a weird issue with menus not working correctly.

Site has a defined menu in Wordpress (WP4.4). Two top level options first up that have no sub-menus, then 3 options that do have sub-menus. Atahualpa is configured to use the menu as the first option.

Issue seems to be that the `rMenu-expand` class gets added to the first menu entry that doesn't contain a sub-item which appears before the menu entry that contains a sub-item (instead of the entry with sub-items). In the case of my site this is the first menu entry "Home".

Site: http://www.hackmelbourne.org (Connected Community Hackerspace in Melbourne, Australia)

Works fine with the twentyfifteen theme, but it doesn't really add a class like this (just sub-items). Have tried with no plugins. Also tried without & in the menu entry title. Also tried recreating the menu entry from scratch. Tried with and without my child theme.

Config attached, but pretty sure this is a code bug. Also attached is a pic of the menu as currently configured in WP. Most items in the menu are Pages, so should be easily reproduced.

FYI: Moving "Blog" after "About CCHS" (and it's sub-items) ends up with a sub-item marker attached to "Blog" as well (the one from "About Rules & Policies" disappears).