The content is visible in the editor, but the Preview is missing some content.

To reproduce

1. I was using the Theme Unit Test data from https://github.com/WPTRT/theme-unit-test/
2. Click to edit the Post titled "Markup: HTML Tags and Formatting"
3. Scroll down to see that the Table follows the Block Quote.
4. Click on Preview.
5. See that there is no Table heading following the Block Quote and the formatting of the rest of the page is for blockquote.

Expected behavior
The preview should match the content in the editor.

Screenshots
This is how it looks in the editor:

And this is how the preview looks:

Desktop

• OS: Ubuntu Studio 16.04
• Browser: Firefox 66.0.2
• WP Version 5.1.1
• no plugins, Twenty Nineteen theme