When a form hangs at submit, there may be a Nonce issue. Especially if the form is large or multi-page.
If you inspect, the console error will look similar to:
If you click on VM163:1 or go to the SOURCES tab you will see:
Nonce expired, please refresh the page. If the error persists please contact the site administrator
This should solve the issue:
If your forms include multiple pages and have a lot of fields in them you may need to increase your max_input_vars to at least 3000 in your PHP.ini and/or wp-config.php settings to prevent a "nonce expired" error or receiving only part of the form during submission.