Networking not sequenced, - ReliableSequenced Qos in Transport Layer API?

Hi there, I'm trying to build a simple server and client application using unity and Transport Layer API. I request QosType.ReliableSequenced for both the client and server app, open up the connection, etc. In my server Update method I increase an int called iClock by 1 every frame and then after that send a message to the client up with the value of iClock like so:

     public void SendPlayerClock(Player player)
     {
         Account account = player.account;
         byte[] buffer;
         byte error;
 
         MemoryStream writeStream = new MemoryStream();
         BinaryWriter writer = new BinaryWriter(writeStream);
         writer.Write(PackageType.Clock);
         writer.Write(iClock);
         buffer = writeStream.ToArray();
 
         NetworkTransport.Send(serverSocketId, player.iConnectionId, rsChannel, buffer, buffer.Length, out error);
     }

In the client I receive the event via NetworkTransport.Receive in its Update method and display the iClock value via OnGui. At first it goes in order, but here's what happens:

1. At first the client sees the value increasing as it should

2. After some time, every once in a while it skips to a lower value and continues, in time it's getting worse and worse

3. If I move the focus away from the Editor, it seems to kind of display the same symptoms, but if I open an instance of a built client and focus on that one, the original one in the editor just stops, doesn't show any change in the counter, as soon as I put the focus back to it, it continues, but now it skips between high and low values.

What is going on? Both the client and the server have the runInBackground set to true. Am I misunderstanding the ReliableSequenced QoS or some threading stuff going on? It seems it's heavily reliable on the framerate of the application.

Here is how I open the socket:

     //Initialize the Unity Transport Layer API
     public void InitializeNetworkCode()
     {
         Debug.Log("Initializing Network Code");
         Application.runInBackground = true;
         // Init Transport using default values.
         NetworkTransport.Init();
        
         // Create a connection config and add a Channel.
         ConnectionConfig config = new ConnectionConfig();
         rsChannel = config.AddChannel(QosType.ReliableSequenced);
 
         // Create a topology based on the connection config.
         HostTopology topology = new HostTopology(config, serverSettings.MaxNumPlayers);
 
         int iChannel = 8801;
         // Create a host based on the topology we just created, and bind the socket to port 12345.
         serverSocketId = NetworkTransport.AddHost(topology, iChannel);
     }

Here is the receiving code:

                NetworkEventType evnt = NetworkTransport.Receive(out outHostId, out outConnectionId, out outChannelId, buffer, bufferSize, out receiveSize, out error);

Edit After some testing I can see that in this scenario, if I change the QoS, the behavior is as follows: Unreliable - least amount of skipping ReliableSequenced - moderate amount of skipping AllCostDelivery - completely crazy

Why is that? How can I have a truly reliable and sequenced way of delivering data?