Connections close with reason: PROTOCOL_ERROR(1002): RSV bit(s) incorrectly set.}

Some connections close with that reason (RSV bit(s) incorrectly set), and I see them trying to reconnect with no success.

At the same time, many users report daily that they can't connect to the websocket server, most of them from non-windows OS (mainly Chromium OS).

The clients connect to the server using HTML5's Js Websocket library.

I can't reproduce the problem as it works in all my devices (Windows, Android and iOS).

What are the RSV bits? And why they may be "incorrectly set"? What can I do to track the root of the problem?

Thanks.
#### Environment
Debian 7.5
#### Affected Versions
[1.14]