nginx add_header not applied to some server contexts

I have several add_header directives in my main http context of the nginx.conf file, such as:

add_header X-Frame-Options "SAMEORIGIN";
add_header X-XSS-Protection "1; mode=block";

There no other such directives in server and location contexts. For some reason, the header is not applied to server contexts. For example, this one:

server {
        server_name my.example.com;
        location / {
            proxy_pass http://192.168.1.1:12345;
        }

        location /robots.txt {
            return 200 "User-agent: *\nDisallow: /\n";
        }

        client_max_body_size 300M;
    
        listen 443 ssl; # managed by Certbot
        ssl_certificate fullchain.pem; # managed by Certbot
        ssl_certificate_key privkey.pem; # managed by Certbot
        include options-ssl-nginx.conf; # managed by Certbot
        ssl_dhparam ssl-dhparams.pem; # managed by Certbot
    }

What could be causing this?

EDIT: nginx version is 1.23.3.

The file options-ssl-nginx.conf in /etc/letsencrypt/ has:

ssl_session_cache shared:le_nginx_SSL:10m;
ssl_session_timeout 1440m;
ssl_session_tickets off;

ssl_protocols TLSv1.2 TLSv1.3;
ssl_prefer_server_ciphers off;
# + one line of ssl_ciphers

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# 答案1
**得分**: 1

如注释中所解释的，向`add_header`指令添加`always`参数可以使标头适用于所有类型的HTTP响应（包括错误），详情请参阅文档：http://nginx.org/en/docs/http/ngx_http_headers_module.html#add_header

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<summary>英文:</summary>

As explained in comment, adding the `always` parameter to the `add_header` directive allows the header to be added for all kind of HTTP responses (errors included), see the doc for more details: http://nginx.org/en/docs/http/ngx_http_headers_module.html#add_header

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