PHP Errors in Ajax Response

{
    "key": "610f05f6a6a4ced522ad66f94187b94d",
    "type": "warning",
    "message": "Undefined array key \"submission_title\"",
    "file": "wp-content/plugins/acf-frontend-form-element/main/frontend/forms/classes/submit.php",
    "line": 501,
    "stack": [
        "Frontend_Admin\\Classes\\Submit_Form->return_form()",
        "Frontend_Admin\\Classes\\Submit_Form->submit_form()",
        "Frontend_Admin\\Classes\\Submit_Form->check_submit_form()",
        "do_action('wp_ajax_frontend_admin/form_submit')"
    ],
    "component": "Plugin: acf-frontend-form-element"
}