This had just happened, I was trying to increase the default timeout of an nginx running in a container for a proxy pass and always got a 504-gateway timeout response. I was setting proxy_connect_timeout, proxy_send_timeout, proxy_read_timeout, send_timeout, keepalive_timeout, etc. and nothing worked, after two hours of adding and removing lines of configuration (and waiting 1 minute for every time I tried a request), then I realized I have a local nginx for redirect server names to local ports (the container), that nginx was the one that actually responds with the 504 error, after that I tried a request with the port of the container ALL WORKED!!!!