Steps to reproduce the issue

Case 1 - without login module
Create an article with a registered access.
Login on frontend to get a direct link to this article. Copy it.
Logout and try to access a copied link as a guest.
Try to login!

Case 2 - with login module
Create and publish a login module in all pages.
Create an article with a registered access.
Login on frontend to get a direct link to this article. Copy it.
Logout and try to access a copied link as a guest.
Try to login!
You'll be redirected to default menu page and not to the article.

Expected result

A com_users component with login form, resulting in a redirect to original page, in this case, the article.

Actual result

You have the message:
"Error
You are not authorised to view this resource."

And just it.

If you don´t have a login module in all pages, the users can´t login.
Even if you publish de login module, the users will be redirected to default menu page.

Additional comments

If the marketing team wants to create a campaign linked to an registered article (in intranets for example), it will be impossible unless they use a third part extension.