Interesting!
Because it’s actually the 404 page and not a homepage.
Not sure how it happened, but here are the screenshots:
You can actually type in any gibberish path on your site and will still see the same “homepage” content:
I guess you may have templates/index.json deleted?
Just started to write that if it works fine for you then simple code edit would fix the tab title, but I think is totally not OK from the SEO point of view, so you may need to reinstall it.
What are your search results?