Drupal Module: Share by Mail Failure in Social Media Share Module
This is a rather otaku (nerdy) error you may find when using the Social Media Share module for D8: when trying to share by mail the browser opens the mail client with an incomplete title and body. Except, it only does it for certain articles. Sounds like a mystery; it's not.
A little background: one of my clients recently put together a blog. On that blog, we were careful to put together a custom styled share block using the Social Media Share module--we run the D8 version (8.x-1.8).