WordPress featured image url rendering incorrectly when page is loaded causing image to break

I’d recommend taking a look at the database.

1) check the upload_path option and correct directly if needed (well, this one can be altered here too: wp-admin/options.php)

SELECT *  FROM `wp_options` WHERE `option_name` = 'upload_path'

2) check the guid of the attachments and use this plugin if needed

SELECT guid,post_mime_type  FROM `wp_posts` WHERE `post_type` = 'attachment'