IPhone Submission Spinner Issue

I have the current version of Contact Form 7 – The form works perfectly on a computer – AJAX submits and page redirects as set up using:
document.addEventListener( ‘wpcf7mailsent’, function( event ) {
window.location.replace(“https://www.<MyDomain&gt;.com/warranty-thankyou/”);}, false );

When form is submitted from iPhone – the email is sent, but the spinner just keeps spinning. No redirect and no indication that the form has submitted properly. – Same page – same form. Users are hitting the Send button repeatedly – resulting in multiple emails sent, but hey never know that the email was sent successfully.

FYI – the page checks with no issues with W3C Markup Validation, Javascript is loading properly.