Upon reviewing the link provided, the Twitter image tag does not contain the absolute URL of the image; instead it contains a relative URL like so:
<meta name="twitter:image" content="/wp-content/uploads/2019/06/filename.jpg" />
A relative URL is not a valid URL for sharing content on social media and may cause issues with search engines. As this does not happen for all URLs on the page, I suspect that you have a plugin that rewrites image URLs to be relative (without a protocol and domain). Please adjust the settings so the image URLs contain the absolute URL of the image (with a protocol and domain).
The fastest way to To determine which plugin or theme causes this behavior is to?deactivate all non-Yoast plugins and switch to a standard theme?like?Twenty Nineteen.?
Test this on your development or staging site, if you have one. If not, we recommend using the?Health Check & Troubleshooting?plugin. This plugin allows you to run a conflict check?without affecting normal visitors to your site.
As we can imagine that you’re unfamiliar with checking for conflicts, we’d like to point you to a step-by-step guide that will walk you through the process:?How to check for plugin conflicts.