The problem came from schema.org references.

[kexej28769@nongnue]

Google was looking at both server-side and client-side markup. However, the server-side aspect took precedence.

Removing the server-served markup means that the 5-star markup has started to appear.

2. Why won't Bing show 5-star canada number data on review pages, when Google does?



This caused the head to expire prematurely and left a non-index tag in the body where it had not been read.

4. Why does any page on a website return a 302 20-50% of the time, but only to crawlers?

It took a while to figure this out. The client had an old legacy website with two servers, one for the blog and one for the rest of the site. The problem started occurring shortly after the blog was moved from a subdomain (blog.client.com) to a subdirectory (client.com/blog/…).

On a superficial level everything was fine. If a user requested an individual page it all looked good. A crawl of all the blog URLs to check that they were redirected was fine.

But we saw a sharp increase in errors being flagged in Search Console, and during a routine site crawl, many pages that were fine when checked manually were causing redirect loops.