502 Bad Gateway nginx on Multisite

Hi John, first of all, thanks a lot for this plugin, an extremly helpful tool.

I was facing a 502 error when updating stuff on the backend, “Save settings” on WP core, theme and plugins, and pinpointed it to Query Monitor. I couldn’t find any relevant error log… The save action is recorded to the DB, btw

My wp-config is as follows:

define('WP_AUTO_UPDATE_CORE', 'minor');
define('DB_NAME', '***');
define('DB_USER', '***');
define('DB_PASSWORD', '***');
define('DB_HOST', '***');
define('DB_CHARSET', 'utf8');
define('DB_COLLATE', '');
define('AUTH_KEY',         '***');
define('SECURE_AUTH_KEY',  '***');
define('LOGGED_IN_KEY',    '***');
define('NONCE_KEY',        '***');
define('AUTH_SALT',        '***');
define('SECURE_AUTH_SALT', '***');
define('LOGGED_IN_SALT',   '***');
define('NONCE_SALT',       '***');
define('JWT_AUTH_SECRET_KEY', '***');
define('JWT_AUTH_CORS_ENABLE', true);
define('WP_DEBUG', true);

if ( WP_DEBUG ) {
    define( 'WP_DEBUG_LOG', false );
    define('WP_DEBUG_DISPLAY', false);
    $path = realpath( $_SERVER["DOCUMENT_ROOT"] . '/..' ) . '/debug.log';
    @ini_set( 'log_errors', 'On' ); 
    @ini_set( 'error_log', $path );
    error_reporting(0);
    @ini_set('display_errors', 0);
}

$table_prefix = '***';
$_SERVER['HTTPS'] = "on";
define('WP_HOME','https://site.com');
define('WP_SITEURL','https://site.com');
/** Define WordPress.com AKISMET API Key */
define('WPCOM_API_KEY','***');
define('FS_METHOD', 'direct');
define('WPLANG', '');
define('WP_MEMORY_LIMIT', '256M');
# define('DISALLOW_FILE_EDIT', true);
define('NOBLOGREDIRECT', 'https://site.com');
define('DISABLE_WP_CRON', true);
define('COOKIE_DOMAIN', false); 
define('ADMIN_COOKIE_PATH', '/');
define('COOKIEPATH', '');
define('SITECOOKIEPATH', '') ; 
# define( 'SUNRISE', 'on' );
define('WP_ALLOW_MULTISITE', true);
define('MULTISITE', true);
define('SUBDOMAIN_INSTALL', true);
define('DOMAIN_CURRENT_SITE', 'site.com');
define('PATH_CURRENT_SITE', '/');
define('SITE_ID_CURRENT_SITE', 1);
define('BLOG_ID_CURRENT_SITE', 1);

And .htaccess:

# BEGIN JWT PLUGIN
RewriteEngine on
RewriteCond %{HTTP:Authorization} ^(.*)
RewriteRule ^(.*) - [E=HTTP_AUTHORIZATION:%1]
# END JWT PLUGIN

# WORDPRESS
RewriteEngine On
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
RewriteBase /
RewriteRule ^index\.php$ - [L]
# uploaded files
RewriteRule ^files/(.+) wp-includes/ms-files.php?file=$1 [L]
# add a trailing slash to /wp-admin
RewriteRule ^wp-admin$ wp-admin/ [R=301,L]
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^(wp-(content|admin|includes).*) $1 [L]
RewriteRule ^(.*\.php)$ $1 [L]
RewriteRule . index.php [L]

Any suggestion on what I could do to further troubleshoot this?

Thanks again!