Duplicate user (when register an user for the first time).

Hi, I’m using this plugin for register user in a e-shop. but when an new user wants to creates his new account says “There was an error in the submitted form” but in fact the site register the user and stay in the register page and show’s the username field and email filed as duplicate.

I assume the form was sent twice, but why? was put just a shortcode in the page, nothing else.

Please Help

https://wordpress.org/plugins/profile-builder/