Several features are not working with clustering, for example the chat:
I can open it, but...
As you see in this screenshot, sometimes I get the messages and sometimes I don't.
Or the plugins, I can initiate installation and nothing happens but the image changes. Installation through the ACP just don't work with clustering. I haven't tested it yet together with websockets, as I'm a cloudflare customer and haven't got access to the websockets right now.