Contact Form: Error sending via ajax

I'm trying to send the form via ajax to the "admin-ajax.php", but gives the error "An error occurred. Please try again later".
I concluded that the code stops at line 2384 of "grunion-contact-form.php". There is a condition: ($ post-> ID! = $ _POST ['contact-form-id']), which results in TRUE, then "return false" is triggered, not completing the send.
The "$post" of the above condition refers to the global variable, but it does not exist in ajax requests by "admin-ajax.php". This must be corrected.

Start in grunion-contact-form.php around line 2384 and trace the admin-ajax.php request path described in the report. Verify how the post data and contact-form-id are handled during an AJAX submission. Done means the form sends successfully through AJAX without triggering the reported error.

Written by the indexing model from the issue text.