Googlebot returns all WordPress Preview ‘Draft’ Pages as 5xx error

The error is: Server error (5xx)

The example URL google search console provides is: https://www.whatisepigenetics.com/rna-methylation-dependent-rna-processing-controls-the-speed-of-the-circadian-clock/?preview=true&preview_id=704&preview_nonce=985d7afa0b

When I Fetch as Google the actual published post, there is no issue.
When I Fetch as Google this and any other preview pages, the same error is returned: (server error (5xx)).

Robots.txt is blocking /wp-admin/ which you need to access in order to be able to view the preview page… Any insight? Is there a way to fix this? How does this impact SEO and pages being indexed?

Thanks for any assistance!

The page I need help with: [log in to see the link]