Getting a Cors error when trying to upload larger files

I have an express nodejs endpoint where im able to upload a file.pdf,xls,txt.

Locally anything works fine but when I host it on my VPS which is running on a reverse proxy with a different origin, im getting a cors error

BUT only if file size is larger than ~15kb, when my file is smaller anything works fine.

I allowed any cors on my nginx

`

location / {

    add_header 'Access-Control-Allow-Origin' '*';

    return 301 https://$server_name$request_uri;

}`

And set my express server the same