Strange Sphinx ARM search results

I'm seeing a weird thing in the Kea RTD ARM: I went to the main page (https://kea.readthedocs.io/en/latest/) and searched for "configuration backend" in the search box. It found 50 pages matching the search query, so I clicked on the first set of responses (https://kea.readthedocs.io/en/latest/config.html?highlight=configuration%20backend), but they all say "SORRY - This page does not exist yet." If I go to the second set of matches (https://kea.readthedocs.io/en/latest/arm/config.html?highlight=configuration%20backend), those work. Why is the first set coming up in the search results if it doesn't work correctly?

And search does work correctly if I go to the 1.6.0 version rather than to "latest."