Hi @Steve,

Thank you for taking my issue under consideration. I think I finally found the bug 😀

It seems that add_action('admin_enqueue_scripts', 'wp_enqueue_media'); in piklist/includes/class-piklist-forms.php overrides the WordPress’s default behaviour. The wp_enqueue_media can be done only once (cf.: media.php#L3220) and in Piklist, you don’t give the post object like in WP (cf.: media.php#L558) when you add this action into admin_enqueue_scripts. I don’t understand the reasons why you did that all the time.

It is possible that this bug breaks also the relation (post_parent) between post and attachment :/

I tried to remove the line into class-piklist-forms.php and it works well.