If you encounter with this problem, e.g. wishlist(2) and when you click on it, you will see blank content, resp. you will see no products, it means that the products are not exist in wordpress. You will have to go to your database and remove that products manually.

You can delete it by this SQL command:

DELETE FROM wp_yith_wcwl WHERE ID IN (SELECT w.ID FROM wp_yith_wcwl as w LEFT JOIN wp_posts as p ON w.prod_id = p.ID WHERE p.post_type IS NULL OR p.post_type <> 'product')

Resp. please change “wp_” to your database prefix.