2 same playerControlerId's

I'm developing Unity multiplayer game. I'm testing my game locally and it all works fine except when new player tries to join game I get this error message:

On host side:

Thereis already a player at that playerControllerId forthis connections.
On client side:

A connection has already been setas ready.There can only be one.
Player are autospawn by NetworkManager, this is code that extends manager to UI.

Code (CSharp):

1. publicclassNetwotkManagerCustom:NetworkManager{
2.  
3.        publicNetworkDiscoveryDiscovery;
4.        publicGameObjectPlayerPrefab;
5.  
6.        publicvoidStartHost(){
7.                SetPort();
8.               NetworkManager.singleton.StartHost();
9.               Discovery.Initialize();
10.               Discovery.StartAsServer();
11.        }
12.  
13.        publicvoidSearchGame(){
14.               Discovery.Initialize();
15.               Discovery.StartAsClient();
16.        }
17.  
18.        publicoverridevoidOnClientConnect(NetworkConnection connection){
19.               ClientScene.AddPlayer(connection,0);
20.        }
21. }

If I "pause" the game when there are both players in the scene(second before error) and if I go to Network Identity of player they both have they identities set to "0".

Why is this error happening?