I am using Gunicorn + Flask + Meinheld + NGINX with egg:meinheld#gunicorn_worker setting but when I try to upload more than 10 MB server fails with 502 Bad Gateway.
I think Meinheld causes the issue because I can upload the same files with sync workers.

Exact error is:

[error] 4338#4338: *1 sendfile() failed (32: Broken pipe) while sending request to upstream, client: 127.0.0.1, server: localhost, request: "POST /******** HTTP/1.1", upstream: "http://127.0.0.1:8000/*********", host: "localhost", referrer: "http://localhost/******/"

Edit: When I disable Gunicorn and use only Meinheld, it works without an error.

Any ideas?