[Plugin: Video Thumbnails] Not working after reinstall

This is happening because the thumbnail URL is saved as a custom field with the post. When deleting the images from the media library, the custom field information is left behind. When scanning past posts, it’s seeing that the custom field already has a URL.

Here’s what you should try. Open the plugin with the editor and look for this section:

function video_thumbnails_past_callback() {
	global $wpdb; // this is how you get access to the database

	$post_id = $_POST['post_id'];

	echo get_the_title($post_id) . ' - ';

	if ( ($video_thumbnail=get_video_thumbnail($post_id)) != null ) {
		echo '<span style="color:green">✔</span> Success!';
	} else {
		echo '<span style="color:red">✖</span> Couldn\'t find a video thumbnail for this post.';
	}

	die();
}

Now replace it with the code below, which adds in the delete_post_meta line:

function video_thumbnails_past_callback() {
	global $wpdb; // this is how you get access to the database

	$post_id = $_POST['post_id'];

	echo get_the_title($post_id) . ' - ';

	delete_post_meta($post_id, '_video_thumbnail');

	if ( ($video_thumbnail=get_video_thumbnail($post_id)) != null ) {
		echo '<span style="color:green">✔</span> Success!';
	} else {
		echo '<span style="color:red">✖</span> Couldn\'t find a video thumbnail for this post.';
	}

	die();
}

This should clear out the custom field before searching. Remove the line once you’re done so that if you ever need to scan old posts again you won’t be doubling images.