Contact Form 7 503 ajax response in maintenance mode (hardcode fix included)

I’ve created my custom

wp-content/wp-maintenance-mode.php

template, which I saw is supported in

init()

function, because in code it looks for this file over at wp-content. SO I added

wp_head();

before end of </head>
and before end of </body> added

_wp_footer_scripts();

to load all necessary js for CF7. After lots of reading, debugging var_dumping, hard-coding I found a hardcode fix. But I would appreciate a long term solution. Because my fix could be removed any update if not looked into, or it should be added to

wp-content/plugins/wp-maintenance-mode/includes/classes/wp-maintenance-mode.php

. So here is the fix:

Find init() function on last mentioned file. In my case line: 419.

At the end or beginning, up to your preferences, of if statement add this validation rule:
&& !intval($_POST[‘_wpcf7_is_ajax_call’]), it can be as well !isset, or !empty, but I found that $_POST[‘_wpcf7_is_ajax_call’] value is always 1, so probably it is like that for a reason, so I left intval validation. As conclusion: this should prevents from loading 503 header and returning

maintenance.php or wp-content/wp-maintenance-mode.php html.

P.S. After changes if statement in init() function should look something like that:
……

public function init() {
            /**
             * CHECKS
             */
            if (
                    (!$this->check_user_role()) &&
                    !strstr($_SERVER['PHP_SELF'], 'wp-cron.php') &&
                    !strstr($_SERVER['PHP_SELF'], 'wp-login.php') &&
                    !strstr($_SERVER['PHP_SELF'], 'wp-admin/') &&
                    !strstr($_SERVER['PHP_SELF'], 'async-upload.php') &&
                    !(strstr($_SERVER['PHP_SELF'], 'upgrade.php') && $this->check_user_role()) &&
                    !strstr($_SERVER['PHP_SELF'], '/plugins/') &&
                    !strstr($_SERVER['PHP_SELF'], '/xmlrpc.php') &&
                    !$this->check_exclude() &&
                    !$this->check_search_bots() &&
                    !intval($_POST['_wpcf7_is_ajax_call'])
            ) {
                // HEADER STUFF

……

https://wordpress.org/plugins/wp-maintenance-mode/