Index: DamEngine/trunk/src/Deltares.DamEngine.TestHelpers/GeneralHelper.cs
===================================================================
diff -u
--- DamEngine/trunk/src/Deltares.DamEngine.TestHelpers/GeneralHelper.cs	(revision 0)
+++ DamEngine/trunk/src/Deltares.DamEngine.TestHelpers/GeneralHelper.cs	(revision 4172)
@@ -0,0 +1,42 @@
+// Copyright (C) Stichting Deltares 2023. All rights reserved.
+// 
+// This file is part of the Dam Engine.
+// 
+// The Dam Engine is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Affero General Public License for more details.
+// 
+// You should have received a copy of the GNU Affero General Public License
+// along with this program. If not, see <http://www.gnu.org/licenses/>.
+// 
+// All names, logos, and references to "Deltares" are registered trademarks of
+// Stichting Deltares and remain full property of Stichting Deltares at all times.
+// All rights reserved.
+
+using System.Collections.Generic;
+using Deltares.DamEngine.Data.Standard.Logging;
+
+namespace Deltares.DamEngine.TestHelpers;
+
+public static class GeneralHelper
+{
+    public static int DetermineNumberOfCalculationErrors(List<LogMessage> calculationMessages)
+    {
+        int errorCount = 0;
+        foreach (var logMessage in calculationMessages)
+        {
+            if ((logMessage.MessageType == LogMessageType.Error) || (logMessage.MessageType == LogMessageType.FatalError))
+            {
+                errorCount++;
+            }
+        }
+
+        return errorCount;
+    }
+}
\ No newline at end of file
Index: DamEngine/trunk/src/Deltares.DamEngine.Calculators/KernelWrappers/MacroStabilityInwards/MacroStabilityInwardsKernelWrapper.cs
===================================================================
diff -u -r4150 -r4172
--- DamEngine/trunk/src/Deltares.DamEngine.Calculators/KernelWrappers/MacroStabilityInwards/MacroStabilityInwardsKernelWrapper.cs	(.../MacroStabilityInwardsKernelWrapper.cs)	(revision 4150)
+++ DamEngine/trunk/src/Deltares.DamEngine.Calculators/KernelWrappers/MacroStabilityInwards/MacroStabilityInwardsKernelWrapper.cs	(.../MacroStabilityInwardsKernelWrapper.cs)	(revision 4172)
@@ -175,7 +175,7 @@
                 macroStabilityOutput.Message = new LogMessage
                 {
                     MessageType = LogMessageType.FatalError,
-                    Message = e.Message
+                    Message = e.Message + " Stack: " + e.StackTrace
                 };
                 kernelDataOutput = macroStabilityOutput;
                 return PrepareResult.Failed;
Index: DamEngine/trunk/src/Deltares.DamEngine.Calculators/KernelWrappers/MacroStabilityCommon/MacroStabilityCommonHelper.cs
===================================================================
diff -u -r4150 -r4172
--- DamEngine/trunk/src/Deltares.DamEngine.Calculators/KernelWrappers/MacroStabilityCommon/MacroStabilityCommonHelper.cs	(.../MacroStabilityCommonHelper.cs)	(revision 4150)
+++ DamEngine/trunk/src/Deltares.DamEngine.Calculators/KernelWrappers/MacroStabilityCommon/MacroStabilityCommonHelper.cs	(.../MacroStabilityCommonHelper.cs)	(revision 4172)
@@ -329,7 +329,7 @@
             var message = new LogMessage
             {
                 MessageType = LogMessageType.FatalError,
-                Message = e.Message
+                Message = e.Message + " stack: " + e.StackTrace
             };
             messages.Add(message);
             if (kernelDataOutput != null)
@@ -382,6 +382,7 @@
         {
             macroStabilityOutput.CalculationResult = CalculationResult.UnexpectedError;
             messages.Add(new LogMessage(LogMessageType.Error, null, e.Message));
+            messages.Add(new LogMessage(LogMessageType.Error, null, e.StackTrace));
         }
     }
 
Index: DamEngine/trunk/src/Deltares.DamEngine.Data/Geometry/Routines2D.cs
===================================================================
diff -u -r4132 -r4172
--- DamEngine/trunk/src/Deltares.DamEngine.Data/Geometry/Routines2D.cs	(.../Routines2D.cs)	(revision 4132)
+++ DamEngine/trunk/src/Deltares.DamEngine.Data/Geometry/Routines2D.cs	(.../Routines2D.cs)	(revision 4172)
@@ -269,37 +269,41 @@
 
             while (index < polygon.CalcPoints.Count)
             {
-                deltaX = polygon[index].X - x;
-                deltaZ = polygon[index].Z - z;
-                absX = Math.Abs(deltaX);
-                absZ = Math.Abs(deltaZ);
-                if ((absX < epsilon) && (absZ < epsilon))
+                if (polygon[index] != null)
                 {
-                    UndoAddIfNeeded(polygon, pointAdded);
-                    return PointInPolygon.OnPolygonEdge;
-                }
+                    deltaX = polygon[index].X - x;
+                    deltaZ = polygon[index].Z - z;
+                    absX = Math.Abs(deltaX);
+                    absZ = Math.Abs(deltaZ);
+                    if ((absX < epsilon) && (absZ < epsilon))
+                    {
+                        UndoAddIfNeeded(polygon, pointAdded);
+                        return PointInPolygon.OnPolygonEdge;
+                    }
 
-                double al2 = Math.Atan2(deltaZ, deltaX);
-                double al3 = al2 - al1;
+                    double al2 = Math.Atan2(deltaZ, deltaX);
+                    double al3 = al2 - al1;
 
-                if (al3 < -Math.PI)
-                {
-                    al3 = al3 + (2.0 * Math.PI);
-                }
+                    if (al3 < -Math.PI)
+                    {
+                        al3 = al3 + (2.0 * Math.PI);
+                    }
 
-                if (al3 > Math.PI)
-                {
-                    al3 = al3 - (2.0 * Math.PI);
-                }
+                    if (al3 > Math.PI)
+                    {
+                        al3 = al3 - (2.0 * Math.PI);
+                    }
 
-                if (((Math.PI - al3) < epsilon) || ((Math.PI + al3) < epsilon))
-                {
-                    UndoAddIfNeeded(polygon, pointAdded);
-                    return PointInPolygon.OnPolygonEdge;
+                    if (((Math.PI - al3) < epsilon) || ((Math.PI + al3) < epsilon))
+                    {
+                        UndoAddIfNeeded(polygon, pointAdded);
+                        return PointInPolygon.OnPolygonEdge;
+                    }
+
+                    som = som + al3;
+                    al1 = al2;
                 }
 
-                som = som + al3;
-                al1 = al2;
                 index++;
             }
 
Index: DamEngine/trunk/src/Deltares.DamEngine.IntegrationTests/IntegrationTests/MultiCoreMacroStabilityTests.cs
===================================================================
diff -u -r4158 -r4172
--- DamEngine/trunk/src/Deltares.DamEngine.IntegrationTests/IntegrationTests/MultiCoreMacroStabilityTests.cs	(.../MultiCoreMacroStabilityTests.cs)	(revision 4158)
+++ DamEngine/trunk/src/Deltares.DamEngine.IntegrationTests/IntegrationTests/MultiCoreMacroStabilityTests.cs	(.../MultiCoreMacroStabilityTests.cs)	(revision 4172)
@@ -71,6 +71,9 @@
         string outputString = engineInterface.Run();
         File.WriteAllText("Output.xml", outputString);
         Output output = DamXmlSerialization.LoadOutputFromXmlString(outputString);
+        int errorCount = GeneralHelper.DetermineNumberOfCalculationErrors(engineInterface.DamProjectData.CalculationMessages);
+        Assert.AreEqual(0, errorCount, "There should be nor errors during the calculation.");
+        Assert.AreEqual(output.Results.CalculationMessages.Length, engineInterface.DamProjectData.CalculationMessages.Count);  
         if (engineInterface.DamProjectData.DamProjectType == DamProjectType.Design)
         {
             Assert.AreNotEqual(null, output.Results.CalculationResults);
@@ -85,7 +88,8 @@
                 numberOfResults += resultSerie.Entries.TimeSerieEntry.Length;
                 foreach (TimeSerieEntriesTimeSerieEntry timeSerieEntriesTimeSerieEntry in resultSerie.Entries.TimeSerieEntry)
                 {
-                    if (!Double.IsNaN(timeSerieEntriesTimeSerieEntry.Value))
+                    if (!Double.IsNaN(timeSerieEntriesTimeSerieEntry.Value) && (timeSerieEntriesTimeSerieEntry.Value > 0) &&
+                        (timeSerieEntriesTimeSerieEntry.Value < 100000))
                     {
                         numberOfRealResults++;
                     }
@@ -115,6 +119,9 @@
         string outputString = engineInterface.Run();
         File.WriteAllText("Output.xml", outputString);
         Output output = DamXmlSerialization.LoadOutputFromXmlString(outputString);
+        int errorCount = GeneralHelper.DetermineNumberOfCalculationErrors(engineInterface.DamProjectData.CalculationMessages);
+        Assert.AreEqual(0, errorCount, "There should be nor errors during the calculation.");
+        Assert.AreEqual(output.Results.CalculationMessages.Length, engineInterface.DamProjectData.CalculationMessages.Count);
         if (engineInterface.DamProjectData.DamProjectType == DamProjectType.Design)
         {
             Assert.IsNotNull(output.Results.CalculationResults);
@@ -129,7 +136,8 @@
                 numberOfResults += resultSerie.Entries.TimeSerieEntry.Length;
                 foreach (TimeSerieEntriesTimeSerieEntry timeSerieEntriesTimeSerieEntry in resultSerie.Entries.TimeSerieEntry)
                 {
-                    if (!Double.IsNaN(timeSerieEntriesTimeSerieEntry.Value))
+                    if (!Double.IsNaN(timeSerieEntriesTimeSerieEntry.Value) && (timeSerieEntriesTimeSerieEntry.Value > 0) &&
+                      (timeSerieEntriesTimeSerieEntry.Value < 100000)) 
                     {
                         numberOfRealResults++;
                     }
Index: DamEngine/trunk/src/Deltares.DamEngine.Calculators/DikesOperational/OperationalCalculator.cs
===================================================================
diff -u -r4132 -r4172
--- DamEngine/trunk/src/Deltares.DamEngine.Calculators/DikesOperational/OperationalCalculator.cs	(.../OperationalCalculator.cs)	(revision 4132)
+++ DamEngine/trunk/src/Deltares.DamEngine.Calculators/DikesOperational/OperationalCalculator.cs	(.../OperationalCalculator.cs)	(revision 4172)
@@ -249,10 +249,16 @@
             // stability where Piping calc is wanted). In that case, do nothing but just skip.
             if (prepareResult == PrepareResult.Successful)
             {
-                PerformOperationalCalculation(
-                    kernelWrapper, kernelDataInput, kernelDataOutput,
-                    damKernelInput, timeStepIndex, timeSerieEntry, out calculationResult,
-                    calculationMessages);
+                lock (kernelWrapper)//"this" makes it single core again ;-).
+                {
+                    lock (damKernelInput)
+                    {
+                        PerformOperationalCalculation(
+                        kernelWrapper, kernelDataInput, kernelDataOutput,
+                        damKernelInput, timeStepIndex, timeSerieEntry, out calculationResult,
+                        calculationMessages);
+                    }
+                }
             }
             else
             {