Developer Proficient in Avada, WordPress, PHP in US Needed ASAP

We urgently need an extremely well-versed developer proficient in Avada, WordPress and PHP. Must be located within the United States. We have completed extensive troubleshooting together with our hosting provider. SiteGround has confirmed the following: The request reaches POST /wp-admin/admin-ajax.php. The AJAX action is fusion_form_submit_ajax. The request consistently returns 500 Internal Server Error on staging and 502 on production. Server logs report: End of script output before headers: admin-ajax.php upstream prematurely closed connection while reading response header from upstream WP_DEBUG_LOG contains no related fatal PHP errors. The staging php_errorlog also contains no related entries. reCAPTCHA has been completely removed from the form for testing, but the issue remains. SiteGround believes the PHP worker is terminating during the execution of the fusion_form_submit_ajax handler before WordPress can return any response headers. Could you please investigate whether there is a known issue in the Avada Forms AJAX handler or advise what additional debugging steps we should perform? We have also spoken to Avada support, and they gave us an unhelpful suggestion to install an SMTP plugin. We did this and the forms still do not work.