Subdomains routed wrong

[albertoZurini]

I don't know if this is a nginx problem or a container problem, but here is the issue I'm facing: I have created a conf template for my static subdomains:

server {
    listen              443 ssl;
    server_name         [sub].domain;
    ssl_certificate     /etc/letsencrypt/live/domain/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/domain/privkey.pem;
    

    root /var/www/[sub].domain;
    index index.html;
    location / {
        try_files $uri $uri/ =404;
    }
}

The problem is that some subdomains redirect to other sites I have configured (in particular the first in alphabetical order, eg. aa.com)

What could be this issue caused by? I've tried running nginx -t but all the configurations I'm running are fine.
Permissions are fine too (for testing purposes I've even tried chmod 777 without any luck).