When I load scenes additively I see the player's object from a different scene than the one I am on, this is my code to change scenes
[Command(requiresAuthority = false)]
public void ChangeScene(string scene, NetworkConnectionToClient conn = null)
{
conn.Send(new SceneMessage { sceneName = this.gameObject.scene.path, sceneOperation = SceneOperation.UnloadAdditive, customHandling = true });
conn.Send(new SceneMessage { sceneName = scene, sceneOperation = SceneOperation.LoadAdditive });
}