But, there is no link. So, I don't know if that JS file would possibly help? If so, could you provide the file or a link to that file?
I also have a similar problem. I have a user registration form that works fine when loading from a page but when inserting the shortcode in a popup window (using the ‘WordPress Pop Up Plugin'), the form can be seen but the user is not added in the backend. It doesn't even seem to be a problem from the front end (which in a way is even worse as the user thinks he/she is now registered).