I was worried that might happen. When the Show Full Post button is clicked, Discourse scrapes the page content from the web page that is associated with the feed item. What you are seeing when the embed truncate setting is disabled it the result of the markup that comes directly from the RSS feed. It sounds like there is some broken markup in the RSS feed that is causing it to display in the way it is.
The easiest way to confirm this would be to visit the RSS feed URL directly with your browser and have a look at its markup. I think you would look for what falls between its <description> tags.
Thank you for your quick reply.
I have also tried another feed without strange markup.
Here is example from another feed: https://grapee.jp/category/animal/feed
“Embed Truncate” Disable:
The broken image is a known problem caused by the <p> tag. It can be fix manually following the instruction from this post .
But the main problem is, it only show a very short description from the RSS feed, not the whole content from the web page.
That feed is only supplying an excerpt of the full post. That is why you only see an excerpt when the embed truncate setting is disabled.
When you do select the embed truncate site setting, Discourse will attempt to pull the full post content from the post’s URL. If the post has broken HTML, Discourse will not be able to pull in the post content. In those cases, clicking the “Show Full Post” button will not pull in the post. When this happens, the user does not receive an error message telling them what the problem is. Possibly an error message should be displayed for this case.