Hi @takuro(湘南), thank you for also sharing this via in-app support.
In the parallel node workflow I observed an issue with the URL, in both of the YouTube URL fields the URL is the same, which could be causing the issue, you'll be required to match it with the value your server in the query parameter node, for the above case, you'll be required to change the URL to url_2 to match it with Lesson2. Also sent you a detailed email.