Exception-when-entering-a-circumflex

Button "Continue" continues without any problems, so it's a minor issue.

System.InvalidOperationException: "Reopen" ist für die Rückgängig-Komponente nicht möglich, während bereits eine andere Komponente geöffnet ist.
at MS.Internal.Documents.UndoManager.Reopen(IParentUndoUnit unit)
at System.Windows.Documents.TextEditorTyping.OpenTypingUndoUnit(TextEditor This)
at System.Windows.Documents.TextEditorTyping.DoTextInput(TextEditor This, String textData, Boolean isInsertKeyToggled, Boolean acceptControlCharacters)
at System.Windows.Documents.TextEditorTyping.TextInputItem.Do()
at System.Windows.Documents.TextEditorTyping.ScheduleInput(TextEditor This, InputItem item)
at System.Windows.Documents.TextEditorTyping.OnTextInput(Object sender, TextCompositionEventArgs e)
at System.Windows.Controls.Primitives.TextBoxBase.OnTextInput(TextCompositionEventArgs e)
at System.Windows.UIElement.OnTextInputThunk(Object sender, TextCompositionEventArgs e)
at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
at System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
at System.Windows.Input.InputManager.ProcessStagingArea()
at System.Windows.Input.TextCompositionManager.UnsafeCompleteComposition(TextComposition composition)
at System.Windows.Input.TextCompositionManager.PostProcessInput(Object sender, ProcessInputEventArgs e)
at System.Windows.Input.InputManager.RaiseProcessInputEventHandlers(ProcessInputEventHandler postProcessInput, ProcessInputEventArgs processInputEventArgs)
at System.Windows.Input.InputManager.ProcessStagingArea()
at System.Windows.Input.TextCompositionManager.UnsafeStartComposition(TextComposition composition)
at System.Windows.Input.TextCompositionManager.PostProcessInput(Object sender, ProcessInputEventArgs e)
at System.Windows.Input.InputManager.RaiseProcessInputEventHandlers(ProcessInputEventHandler postProcessInput, ProcessInputEventArgs processInputEventArgs)
at System.Windows.Input.InputManager.ProcessStagingArea()
at System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
at System.Windows.Interop.HwndKeyboardInputProvider.ProcessTextInputAction(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at System.Windows.Interop.HwndSource.OnPreprocessMessage(Object param)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)