Google SERP Overriding Title Tag (Unusual)

[n3m3s1z]

I understand that Google can sometimes see your META title tag as merely a suggestion and can show whatever it thinks should be the title based on several factors.

This case is different (I think at least).

A couple things:
It's a wordpress site.
Using Yoast SEO plugin

Example:
Actual title tag on this particular page is "Service Treatment"
Showing on Google SERP "Service Treatment - Name of Site City"

Another page:
Actual title tag is "Service Treatment - Info"
Showing on Google SERP: "Service Treatment - Name of Site City" (Doesn't include the "Info" part of the title tag but adds the Site name)

Yoast setting for title tag separators: | (Not the - that is being shown in SERP)

Has "Name of site" in Schema:
@type: WPHeader
Headline: Name of Site City

Other places where "Name of Site City" is.

<meta property="og:site_name" content="Name of Site City" />
<link rel="alternate" type="application/rss+xml" title="Name of Site City feed" href="https://domain.com/feed" />
<link rel="alternate" type="application/rss+xml" title="Name of Site City Comments Feed" href="https://domain.com/comments/feed" />
<link rel="alternate" type="application/rss+xml" title="Name of Site City Page Comments Feed" href="https://domain.com/page/feed" />

Any ideas as to what in the world is happening here?

Thanks!

[Writerly]

I've read about this and I am really not sure why this is occurring. It could be just one of Google's tests. Other explanation could be that they are ignoring the page title that they perceive as less relevant, or they are just paying more attention to the title tag and, subsequently, change it if necessary.

[tedois]

Looking from a Google perspective, having a short title would make SERP's layout to look weird, so they managed to figure something out to put there. Does that also happen on mobile?

Now, as an SEO, I think it should not be hard to find out where it got that information from. Did you try enhancing those titles further to see what happens?

[buckworks]

I have seen Google rewrite titles before. In the instances I saw, Google was getting the "extra" info from the anchor texts of links pointing to the page.

After we edited the anchor texts, the titles went back to normal..