I have a site that had a Rockettheme Gantry-based theme installed. I'm changing it to a different theme that no longer uses Gantry. The changeover has for the most part been smooth and predictable - just swapping modules to new template positions, but I have one issue I cannot solve - on the home page, and only the home page, I get a system message "Warning - Gantry 5 Component: Cannot display content; not in Gantry 5 template!".
I've checked and double-checked, but there are no Gantry components used anywhere on the home page, nor are there any Gantry particles on the site at all. The old Gantry template is completely uninstalled and the new non-Gantry one assigned to all pages. And the most frustrating part is if I completely disable Gantry plugins and modules and components then the home page and ONLY the home page goes straight to a 404 error. Internal pages still work just fine.