Server Move: All pages leading home

Your proxy is rewriting everything to index.php, which means that the backend never sees the original URI. The proxy should be transparent, like this:

server {
   listen 80;

   server_name example.com;

   location / {
     proxy_set_header X-Real-IP  $remote_addr;
     proxy_set_header X-Forwarded-For $remote_addr;
     proxy_set_header Host $host;
     proxy_pass http://127.0.0.1:8080;
   }
}