Nginx throwing 404 errors when assets from subfolder of the root are requested

My nginx config file looks like:

passenger_enabled on;
passenger_ruby /home/inspection/.rbenv/shims/ruby;
rails_env    production;

root         /home/inspection/app/current/public;

location /build/ {
root /home/inspection/app/current/public;
autoindex off;
}

if (-f $document_root/under_maintenance.html) {
        return 503;
}
error_page 503 @maintenance;
location @maintenance {
        rewrite ^(.*)$ /under_maintenance.html break;
}

# redirect server error pages to the static page /50x.html
error_page   500 502 503 504  /50x.html;
location = /50x.html {
        root   html;
}

But none of the assets inside the build directory are coming and giving 404. for e.g. https://docking-new.dockingpro.com/build/static/js/runtime-main.1f1f19a3.js if you try you see 404 error.

All files that are inside root folder directly are accessible.

What I need to change here?

The error seem to be in location /build/ When you specify a root inside a location block, Nginx concatenates the root path and the requested URI to generate the final path. Lets remove the root directive from the location /build/ block

Here is your updated code:

passenger_enabled on;
passenger_ruby /home/inspection/.rbenv/shims/ruby;
rails_env    production;

root         /home/inspection/app/current/public;

location /build/ {
    autoindex off;
}

if (-f $document_root/under_maintenance.html) {
    return 503;
}
error_page 503 @maintenance;
location @maintenance {
    rewrite ^(.*)$ /under_maintenance.html break;
}

# redirect server error pages to the static page /50x.html
error_page   500 502 503 504  /50x.html;
location = /50x.html {
    root   html;
}

restart sudo systemctl restart nginx and it should work.