Managed MQTT client hangs when trying to disconnect using `StopAsync()` in Unity Engine about mqttnet HOT 5 OPEN

// NOT in Unity Engine
using MQTTnet;
using MQTTnet.Client;
using MQTTnet.Extensions.ManagedClient;

namespace TestProject1;

public class Tests
{
    [SetUp]
    public void Setup()
    {
    }

    [Test]
    public void Test1()
    {
        // https://github.com/dotnet/MQTTnet/wiki/Client#client-options
        var options = new MqttClientOptionsBuilder()
            .WithTcpServer("broker.emqx.io", 1883)
            .Build();

        var managedOptions = new ManagedMqttClientOptionsBuilder()
            .WithClientOptions(options)
            .Build();

        var mqttFactory = new MqttFactory();
        var client = mqttFactory.CreateManagedMqttClient();
        var task = client.StartAsync(managedOptions);
        task.Wait();
        task = client.StopAsync(cleanDisconnect: false);
        task.Wait();

        Assert.Pass();
    }
}

// Unity Engine testing with NUnit
using NUnit.Framework;
using UnityEngine;
using MQTTnet;
using MQTTnet.Client;
using MQTTnet.Extensions.ManagedClient;


namespace MyProject.Core.Tests
{
    public class MqttNetTests
    {
        /// <summary>
        /// Test the mqttnet library on its own.
        /// </summary>
        [Test]
        public void MqttNetStopAsync()
        {
            // Set up MQTT client
            var options = new MqttClientOptionsBuilder()
                .WithTcpServer("broker.emqx.io", 1883)
                .Build();

            var managedOptions = new ManagedMqttClientOptionsBuilder()
                .WithClientOptions(options)
                .Build();

            var mqttFactory = new MqttFactory();
            var client = mqttFactory.CreateManagedMqttClient();

            // Connect
            var task = client.StartAsync(managedOptions);
            task.Wait();
            Debug.Log("MQTT client started.");

            // Disconnect
            task = client.StopAsync(cleanDisconnect: false);
            task.Wait(); // HANGS
            Debug.Log("MQTT client stopped.");

            Assert.Pass();
        }
    }
}