Such silent error usually a sign of the broken content filters. Content filters are applied to the post text before displaying it. They used by WordPress and third party plugins to beautify and process some formatting tags like shortcodes. Some incorrectly written plugins assume that content filters are applicable only for displaying post so they simply kill execution if applied for any other reasons (like preparing the text for autoposting)

Please go to the plugin settings, scroll to the Debug/Report Settings and check the checkbox titled “My Content Filters (apply_filters(‘the_content’) are broken, don’t use them”

Note: This will make %EXCERPT% work as %RAWEXCERPT%, %FULLTEXT% as %RAWTEXT%, etc…