AWeber + Modal = no redirects

[helgatheviking]

I need some help resolving Case #2185 regarding a conflict between Ninja Forms Modal and Ninja Forms Aweber.

An AWeber form without modal, redirects correctly.
A Modal form without AWeber, redirect correctly.
However, a modal form with AWeber does not redirect when the form is submitted. The modal window simply closes, though the email is sent to AWeber.

The Aweber signup happens on the following hook:

add_action( 'ninja_forms_process', array( $this, 'check_for_email_signup' ), 20 );

I don't know enough about Modal to know why this would cause problems and feel like I am just spinning my wheels here.

[helgatheviking]

Switching to default 10 priority seems to resolve the issue for my test site:
http://sandbox.kathyisawesome.com/ninja-modal/

but not for the customer
http://pvatestsite.com/bbd4life/

[helgatheviking]

Additionally, any errors caused by the AWeber signup are ignored and the modal is closed.