Index: Ringtoets/ClosingStructures/src/Ringtoets.ClosingStructures.Plugin/ClosingStructuresPlugin.cs
===================================================================
diff -u -r183d1e7ed095ea4e8024068bc4ddfcf3ac6997d3 -rb1712af5a19e0e5fa7037e14f61d9d9496483bfa
--- Ringtoets/ClosingStructures/src/Ringtoets.ClosingStructures.Plugin/ClosingStructuresPlugin.cs	(.../ClosingStructuresPlugin.cs)	(revision 183d1e7ed095ea4e8024068bc4ddfcf3ac6997d3)
+++ Ringtoets/ClosingStructures/src/Ringtoets.ClosingStructures.Plugin/ClosingStructuresPlugin.cs	(.../ClosingStructuresPlugin.cs)	(revision b1712af5a19e0e5fa7037e14f61d9d9496483bfa)
@@ -524,11 +524,12 @@
             var parentGroupContext = (ClosingStructuresCalculationGroupContext) parentNodeData;
 
             parentGroupContext.WrappedData.Children.Remove(context.WrappedData);
+            var closingStructuresCalculations = context.FailureMechanism.Calculations.Cast<StructuresCalculation<ClosingStructuresInput>>().ToArray();
             foreach (var calculation in context.WrappedData.GetCalculations().Cast<StructuresCalculation<ClosingStructuresInput>>())
             {
                 StructuresHelper.Delete(context.FailureMechanism.SectionResults,
                                         calculation,
-                                        context.FailureMechanism.Calculations.Cast<StructuresCalculation<ClosingStructuresInput>>());
+                                        closingStructuresCalculations);
             }
 
             parentGroupContext.WrappedData.Children.Remove(context.WrappedData);