No notification is sent, error in php log

No notification sent, but i get this error:

2021/03/14 23:18:31 [error] 79606#79606: *634454 FastCGI sent in stderr: “PHP message: PHP Warning: call_user_func_array() expects parameter 1 to be a valid callback, first array member is not a valid class name or object in /www/…/public/wp-includes/class-wp-hook.php on line 294” while reading response header from upstream, client: 93.40.127.208, server: http://www.xx.com, request: “GET /wp-admin/post.php?post=3487&action=edit HTTP/1.0”, upstream: “fastcgi://unix:/var/run/php7.3-fpm-….sock:”, host: “www.xxx.com”, referrer: “https://www.xxx.com/wp-admin/post.php?post=3487&action=edit”