Nginx Websocket proxy dropping frames

[FlappySocks]

Connecting to my websocket server directly works (Chrome or Firefox).
Connecting via the Nginx websocket proxy connects, but drops frames. Here is
an example of the JSON messages:

<-- {"login" : { "username": "user", "password" : "pass"}}
--> {"loginReply" : { "state": "ok"}}
<-- {"someSetting1" : { "something": "something"}}
<-- {"someSetting2" : { "something": "something"}}  **DROPPED**
<-- {"someSetting3" : { "something": "something"}}  **DROPPED**

Those last three messages are sent immediately after login, but the last two
don't make it to the websocket server (~90% of the time). Subsequent
messages, work fine, as if nothing was missing.

I have tried Nginx 1.4.7, 1.5.13 & 1.6

location /websocket {
            proxy_pass http://localhost:8001;
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection "upgrade";
            proxy_read_timeout 86400;
}

I have tried proxy_buffering off and on.

Anything else I should try?

The problem occurs ~30% of the time on my powerful x86 machine, and ~90% on
my two less powerful ARM machines (one is a Raspberry Pi, and the other a
much faster dual core).

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,249575,249575#msg-249575