Echo rss post to feed

Hi, I have created a "post to RSS" feed via echo RSS. Now I want to edit this feed via the plugin "RSS transmute" and import it back via Echo RSS. Is that possible? I got an error: [26-Oct-2022 13:58:46 UTC] Error in parsing RSS feed (custom method): cURL error 22: The requested URL returned error: 400 for website [26-Oct-2022 13:58:46 UTC] Exception thrown Failed: website