Please provide links to a few pages on your site that are not working.
Here’s one: http://www.humortimes.com/57386/ripping-headlines-today-081516/
This one has a ‘custom’ title I put in, not the regular formula I set up in Yoast SEO, which is title, author, and ‘Humor Times’… For this, one I just put the text in the SEO Title: “Ripping the Headlines Today – Paul Lander, Humor Times”
So, as it should, for FB and Google shares it shows:
Ripping the Headlines Today – Paul Lander, Humor Times
But for Twitter, it gives the regular post title:
Ripping the Headlines Today, 8/15/16
Here’s another: http://www.humortimes.com/57369/american-people-want/
Should say, as per the formula:
What the American People Want – Will Durst, Humor Times
But for Twitter shares, I get only:
What the American People Want
The source code is correct and Twitter does receive the correct title according to their card validator.
I suspect the problem is with the social buttons on your site as the Twitter share button has a custom link that includes it’s own title. Please contact the developer of the social button plugin for advice on how to change their title.