I have the same issue and I think I know how to fix it except that I can not find what is the correct URL I should use with Better Security.
The old URL in the email is something like that:
https://www.mywebsitre.com/wp-admin/post.php?post=1234&action=edit
(so the editor can simply click on the link and was (before WPBS) sent to the post to approve.)
Does anyone knows what should be the new URL (with the private key I assume), I have try:
https://www.mywebsitre.com/wp-admin/post.php?%5Bprivatekey%5D?post=1234&action=edit [still 404]