Can you share -removing sensitive data- the /etc/yunohost/app/wordpress/settings.yml ?
Two possible workarounds to upgrade: either without backup (option -b in CLI) or after recreating the /etc/php/8.4/fpm/pool.d/wordpress.conf/etc/php/8.4/fpm/pool.d/wordpress.conf. See here : WordPress install went bad Now getting a 502 bad gateway and no way to reverse - #14 by xabi