In the file: pro-sites/pro-sites-files/gateways/gateway-stripe.php
add_action( 'wp_head', array( 'ProSites_Gateway_Stripe', 'checkout_js' ) );
Problemo for humming bird...checkout_js is jquery and if you load jquery below so that google page speed ranks you higher, ect then we get a problem...cause checkout_js is loading before and not making sure jquery has been loaded.
So..it needs to be re-written properly to wait for jquery and not be forced in the head of the file (why load it there? no comprende)
Anyways...this is broken...and unnecessarily bad word press coding standards.
But shoot...what do I know.