Index: Ringtoets/HeightStructures/src/Ringtoets.HeightStructures.Plugin/HeightStructuresPlugin.cs
===================================================================
diff -u -r60233a739e6b40a3182f53bb9ebd923703bd745c -rb1712af5a19e0e5fa7037e14f61d9d9496483bfa
--- Ringtoets/HeightStructures/src/Ringtoets.HeightStructures.Plugin/HeightStructuresPlugin.cs	(.../HeightStructuresPlugin.cs)	(revision 60233a739e6b40a3182f53bb9ebd923703bd745c)
+++ Ringtoets/HeightStructures/src/Ringtoets.HeightStructures.Plugin/HeightStructuresPlugin.cs	(.../HeightStructuresPlugin.cs)	(revision b1712af5a19e0e5fa7037e14f61d9d9496483bfa)
@@ -504,11 +504,12 @@
             var parentGroupContext = (HeightStructuresCalculationGroupContext) parentNodeData;
 
             parentGroupContext.WrappedData.Children.Remove(context.WrappedData);
+            var heightStructuresCalculations = context.FailureMechanism.Calculations.Cast<StructuresCalculation<HeightStructuresInput>>().ToArray();
             foreach (var calculation in context.WrappedData.GetCalculations().Cast<StructuresCalculation<HeightStructuresInput>>())
             {
                 StructuresHelper.Delete(context.FailureMechanism.SectionResults,
                                         calculation,
-                                        context.FailureMechanism.Calculations.Cast<StructuresCalculation<HeightStructuresInput>>());
+                                        heightStructuresCalculations);
             }
             parentGroupContext.NotifyObservers();
         }