Index: Core/Common/src/Core.Common.Gui/Forms/ProgressDialog/ActivityProgressDialog.cs
===================================================================
diff -u -r67284323e2785c651633d9c52049ba12a9c70e6a -r0be4ede909cda20598ffd400f452e08c99089bcb
--- Core/Common/src/Core.Common.Gui/Forms/ProgressDialog/ActivityProgressDialog.cs	(.../ActivityProgressDialog.cs)	(revision 67284323e2785c651633d9c52049ba12a9c70e6a)
+++ Core/Common/src/Core.Common.Gui/Forms/ProgressDialog/ActivityProgressDialog.cs	(.../ActivityProgressDialog.cs)	(revision 0be4ede909cda20598ffd400f452e08c99089bcb)
@@ -157,6 +157,8 @@
 
         private void RunActivity(int stepNumberForProgressNotification, int activityCount)
         {
+            runningActivity.LogMessages.Clear();
+
             if (InvokeRequired)
             {
                 UpdateActivityStepControlsDelegate updateDelegate = UpdateProgressControls;
Index: Ringtoets/Piping/src/Ringtoets.Piping.Service/PipingCalculationActivity.cs
===================================================================
diff -u -r81fa8a9bf3bd503cbd280e88b8f6037a840cff12 -r0be4ede909cda20598ffd400f452e08c99089bcb
--- Ringtoets/Piping/src/Ringtoets.Piping.Service/PipingCalculationActivity.cs	(.../PipingCalculationActivity.cs)	(revision 81fa8a9bf3bd503cbd280e88b8f6037a840cff12)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Service/PipingCalculationActivity.cs	(.../PipingCalculationActivity.cs)	(revision 0be4ede909cda20598ffd400f452e08c99089bcb)
@@ -74,7 +74,6 @@
                 return;
             }
 
-            LogMessages.Clear();
             PipingDataSynchronizationService.ClearCalculationOutput(calculation);
 
             PipingCalculationService.Calculate(calculation);