@pcnador
We would like some more information.
1. Can you confirm you are using the most recent Yoast SEO, v12.6? If you update, does the issue resolve?
2.Are all your non-Yoast plugins and themes also updated?
If all are updated and the issue still happens we are not able to reproduce this. We have Classic Editor v1.5 active and were able to add a media item such as a picture on a post. See images: https://pasteboard.co/IIuFp7b.png and https://pasteboard.co/IIuFErq.jpg.
In that case, it sounds like a plugin or theme conflict. Please Check for conflicts.
If there is a conflict with a plugin or a theme, you can create a new GitHub issue?for our developers. Please report the issue to a third party developer as well.
If you didn’t find any conflicts or errors, we think the issue is specific to your site. We’d need to investigate further but are unable to do so on these forums. You can purchase Yoast SEO Premium?and receive our Premium email support and we can help you further.
@gror @sourceline @vencavev @moens
If you are still experiencing the issue per the forum guidelines, we ask that you please create separate topics for the issues you are experiencing. That way it’s easier to track issues and provide assistance on your specific concerns on your specific site. Plus, you will get your own alerts for the issue rather than someone else’s. You may make a new topic here: https://www.ads-software.com/support/plugin/wordpress-seo/#new-post. Thanks!