MQTT library returning error connecting to mosquitto

I am using my Espruino Wifi updated to 2v21. I have a strange problem, although I have used the MQTT library before without any problems, it seem to error for me now. I am able to connect and use tinyMQTT but I want to use QoS > 0 which is only available in MQTT.

I am running mosquitto in a container on my raspberrypi. If I try to connect using the MQTT library I get the following output:

Log from the mosquitto container:
1708970867: New connection from 192.168.1.100:44538 on port 8883.
1708970867: New client connected from 192.168.1.100:44538 as 29004900-0c513532-39333638 (p2, c1, k60, u'username').

Log from Espruino IDE:
Connection refused, unknown return code: NaN.

Here is the code for the MQTT example:

const WIFI_NAME = "BT-redacted";
const WIFI_OPTIONS = { password : "redacted" };
const wifi = require("Wifi");
let mqtt;

const server = "192.168.1.77"; // the ip of your MQTT broker
const options = {
  client_id: getSerial(),
  keep_alive: 60,
  port: 8883,
  clean_session: true,
  username: "username",
  password: "password",
  protocol_name: "MQTT",
  protocol_level: 4,
};

const onInit = () => {
  connect();
};

const connect = () => {
  console.log("wifi connecting...");
  wifi.connect(WIFI_NAME, WIFI_OPTIONS, (err) => {
    if (err) {
      console.log("wifi error", err);
      return;
    }
    console.log("wifi connected");
    connectMQTT();
  });
};

const connectMQTT = () => {
  console.log("connecting to mqtt");
  mqtt = require("MQTT").create(server, options);

  mqtt.on("connected", () => {
    console.log("mqtt connected");
    mqtt.subscribe("espruino/rgb");
    mqtt.subscribe("espruino/speed");
  });

  mqtt.on("publish", (pub) => {
    console.log(pub.topic, pub.message);
  });

  mqtt.on("error", (err) => console.log("error", err));
  mqtt.connect();
};

Full output in Espruino IDE

 ____                 _
|  __|___ ___ ___ _ _|_|___ ___
|  __|_ -| . |  _| | | |   | . |
|____|___|  _|_| |___|_|_|_|___|
         |_| espruino.com
 2v21 (c) 2023 G.Williams
>
>onInit()
wifi connecting...
=undefined
wifi connected
connecting to mqtt
error Connection refused, unknown return code: NaN.
> 

What could be different about MQTT v tinyMQTT for me now?