I'm trying to debug Soft 404 errors in Search Console. The Soft 404's keep appearing. If I try to "Fetch as Google" it seems like they returns a valid response.
HTTP/1.1 200 OK Server: TornadoServer/4.2.1 Content-Type: text/html; charset=UTF-8 Strict-Transport-Security: max-age=31536000 Date: Mon, 14 Mar 2016 14:13:18 GMT
The page is a regular page in a Tornado application showing a full screen with google maps and a navigation header. Google explanation of Soft 404 is:
[...] server returns a code other than 404 or 410 for a non-existent page (or redirecting users to another page, such as the homepage, instead of returning a 404). This creates a poor experience for searchers and search engines.
This page is, however, existing... (and fetches correctly through Search Console). What can cause these Soft 404s?