Peprhaps it is a NGINX config problem? Running drupal in a subdirectory under Apache normally req. you to alter .htacess and RewriteBase. I am not a NGINX admin but I would start by getting a copy of the running config. It might need stuff along

location ~ \.php$ {
        fastcgi_split_path_info ^(/abc)(/.*)$;
}

To avoid loosing in base directory.

Perhaps it is a NGINX config problem? Running Drupal in a subdirectory under Apache normally requires you to alter .htaccess and RewriteBase. I am not a NGINX admin but I would start by getting a copy of the running config. It might need stuff along

location ~ \.php$ {
        fastcgi_split_path_info ^(/abc)(/.*)$;
}

To avoid loosing in base directory.