Fix broken images for posts created by the WP Discourse and RSS plugins

The problem may be that Discourse is not able to find any content on the WordPress page. I wouldn’t expect this to cause a loop though. Discourse should just fail silently if it can’t find any content on the page. Just in case you are testing this with a post that has no real content, try creating a post with some actual text content and see if that makes a difference. You might also want to look into How to configure the allowed embed selectors setting. The allowed embed selectors setting can be used to help Discourse find the page’s content.

Are you using the Block Editor to publish your WordPress posts? If so, how are the images being added to the posts? Are you using a plugin that adds custom image blocks?

Does the post excerpt that it loads include the post’s images?

I wouldn’t expect the excerpt to be automatically loaded here. What I would expect is for the “Show Full Post” button to be displayed. Clicking that button should load the excerpt. When full post content is published from WordPress to Discourse, you can prevent the “Show Full Post” button from being displayed by disabling the Discourse embed truncate site setting.

This might be a good solution for you. Have a look at WP Discourse template customization for details about how to customize the template that’s used to publish posts. There is an example template for publishing the post as a onebox here.