Index: binaries/data/mods/public/gui/common/network.js
===================================================================
--- binaries/data/mods/public/gui/common/network.js
+++ binaries/data/mods/public/gui/common/network.js
@@ -74,6 +74,9 @@
 	case 7: return translate("Playername in use. If you were disconnected, retry in few seconds");
 	case 8: return translate("Server full");
 	case 9: return translate("Secure lobby authentication failed. Join via lobby");
+	case 10: return translate("Error: Server failed to allocate a unique identifier.");
+	case 11: return translate("Error: Client commands were ready for an incorrect game turn.");
+	case 12: return translate("Error: Client simulatedan incorrect game turn.");
 	default:
 		warn("Unknown disconnect-reason ID received: " + id);
 		return sprintf(translate("\\[Invalid value %(id)s]"), { "id": id });
Index: source/network/NetHost.h
===================================================================
--- source/network/NetHost.h
+++ source/network/NetHost.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2017 Wildfire Games.
+/* Copyright (C) 2018 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -56,6 +56,7 @@
 /**
  * Reasons sent by server to clients in disconnection messages.
  * Must be kept in sync with binaries/data/mods/public/gui/common/network.js
+ * To help debugging, use a separate reason for each callstack leading to a disconnect.
  */
 enum NetDisconnectReason
 {
@@ -68,7 +69,10 @@
 	NDR_BANNED,
 	NDR_PLAYERNAME_IN_USE,
 	NDR_SERVER_FULL,
-	NDR_LOBBY_AUTH_FAILED
+	NDR_LOBBY_AUTH_FAILED,
+	NDR_GUID_FAILED,
+	NDR_INCORRECT_READY_TURN_COMMANDS,
+	NDR_INCORRECT_READY_TURN_SIMULATED
 };
 
 class CNetHost
Index: source/network/NetServer.cpp
===================================================================
--- source/network/NetServer.cpp
+++ source/network/NetServer.cpp
@@ -910,7 +910,7 @@
 	{
 		if (++count > 100)
 		{
-			session->Disconnect(NDR_UNKNOWN);
+			session->Disconnect(NDR_GUID_FAILED);
 			return true;
 		}
 		guid = ps_generate_guid();
Index: source/network/NetServerTurnManager.cpp
===================================================================
--- source/network/NetServerTurnManager.cpp
+++ source/network/NetServerTurnManager.cpp
@@ -58,7 +58,7 @@
 			turn,
 			m_ClientsReady[client] + 1);
 
-		session.Disconnect(NDR_UNKNOWN);
+		session.Disconnect(NDR_INCORRECT_READY_TURN_COMMANDS);
 	}
 
 	m_ClientsReady[client] = turn;
@@ -106,7 +106,7 @@
 			turn,
 			m_ClientsReady[client] + 1);
 
-		session.Disconnect(NDR_UNKNOWN);
+		session.Disconnect(NDR_INCORRECT_READY_TURN_SIMULATED);
 	}
 
 	m_ClientsSimulated[client] = turn;