I am testing a new website with social login. I am using Facebook, Twitter, G+, and WP logins. I tested all of them, and Twitter has an issue.
First, I have the plugin set to require an email, and ask for one if one does not exist:
When I login with Twitter for the first time, it creates a new user, even though I have an existing user with the same email address, and it doesn't use the email address I have in Twitter: