Expand/collapse icon missing on mobile menu sub-level menus

I’m trying Bricks and am struggling to get the mobile menu working properly. I have a top level menu item that has a submenu and so has an expand/collapse icon. In the submenu there is an item that also has a submenu but that item does not have an icon and the submenu items are just listed underneath. You can see this in the attached image, the submenu item ‘Fellowship’ has a submenu containing 4 items but there is no icon.

There must be something I am doing wrong as this seems a basic requirement.