Kryonet - one listener, two connections - one is somehow performing slower.

Hello guys! I won’t post all of the code, I will just write an example, cause it is too big and wouldn’t be useful.
I’m facing a strange problem since yesterday. I am implementing my own reliable UDP, sending lists of packets, clearing history of packets, doesn’t matter.

I have two Clients (their code is identical) with one exception - one is starting on the left side, one on the right side of the board. It has nothing to do with packets later.

Also, I have a Server with a gameroom where I pass these two players when they both connect:

public Character player_left, player_right;
public Connection pleft_connection, pright_connection;
public Listener gameRoomListener;

public GameRoom(Connection pleft, Connection pright) { 
		player_left = new Character(1);
		player_right = new Character(2);
		this.pleft_connection = pleft;
		this.pright_connection = pright;
		System.out.println("Sending who is starting left...");
		CasualGameReady out = new CasualGameReady();
		out.startingLeft = true;
		out.startingLeft = false;


As you can see above, I pass two connections and assing them to new ones, to use them in the Gameroom.
Next, we call ‘addListener()’ method which adds a listener to these connections:

public void addListener(){
		gameRoomListener = new Listener() 
			public void received (Connection c, Object object)
					if(object instanceof RequestUnlockingControllers)
					if(object instanceof someObject)
				}else if(c.equals(pright_connection)){
					if(object instanceof RequestUnlockingControllers)
					if(object instanceof someObject)
			public void disconnected (Connection c)

I connect two clients from the same PC to the server on the same PC. I use LAN IP address, to force the client to connect with a router and come back.

So both clients connect with ‘’.
Everything is okay and everything is working really fine with one exception:
one of the connections is slower!

I have some methods, which send player positions in lists and server gives back an info:
‘you can delete positions with sequence number lower than x, they are not needed anymore’.

And somehow, one ‘history list of packets’ is still 2-5 units bigger (one connection is processing slower), than second. Randomly, once left client, once right.
The only solution (cause I have tested ALL) is that server is slower on one of these two connections.
It is impossible, that the client causes the errors, cause both clients are IDENTICAL - they have same code.
Same thing on the server, both:
blocks are identical - with only one keyword changed in every statement (player_left to player_right and vice versa).
Both objects player_left and player_right are also identical so it has to be the listener/connection fault.

Is the code above with attaching listeners, connections etc. correct? Or maybe there is a noobish mistake?
Cause if it is correct, bug has to be somewhere in the code.
If someone has any thoughts, ideas - I will take everyhing.

Thank you very much.