diff --git a/app/TaskFlow/ClassControlCreator.vb b/app/TaskFlow/ClassControlCreator.vb
index 428cd5d..c0763dd 100644
--- a/app/TaskFlow/ClassControlCreator.vb
+++ b/app/TaskFlow/ClassControlCreator.vb
@@ -804,7 +804,6 @@ Public Class ClassControlCreator
 
     Public Function GridTables_GetRepositoryItemForColumn(pColumnName As String, pDataTable As DataTable, pIsAdvancedLookup As Boolean) As RepositoryItem
         If pIsAdvancedLookup Then
-
             Dim oEditor = New RepositoryItemLookupControl3
 
             If pDataTable IsNot Nothing Then
@@ -813,18 +812,34 @@ Public Class ClassControlCreator
                 oEditor.DataSource = pDataTable
             End If
 
+            ' Erlaube ungültige Werte (verhindert automatisches Löschen)
+            oEditor.NullText = "[Ungültiger Wert]"
+            oEditor.ShowFooter = False
+            oEditor.AllowNullInput = DefaultBoolean.True
+            oEditor.ValidateOnEnterKey = True
+
+            ' KRITISCH: Erlaube Texteingabe für ungültige Werte
+            oEditor.TextEditStyle = TextEditStyles.Standard
+
+            ' Weitere Standard-Eigenschaften für LookupControl3
+            'oEditor.ImmediatePopup = False
+
             Return oEditor
         Else
             Dim oEditor = New RepositoryItemComboBox()
             Dim oItems As New List(Of String)
 
-            AddHandler oEditor.Validating, Sub(_sender As ComboBoxEdit, _e As CancelEventArgs)
-                                               If oItems.Contains(_sender.EditValue) Then
-                                                   _e.Cancel = False
-                                               Else
-                                                   _e.Cancel = True
-                                               End If
+            ' KRITISCH: Erlaube Anzeige ungültiger Werte
+            oEditor.TextEditStyle = TextEditStyles.Standard  ' Statt DisableTextEditor!
+            oEditor.AllowNullInput = DefaultBoolean.True
+            oEditor.ValidateOnEnterKey = True
 
+            AddHandler oEditor.Validating, Sub(_sender As ComboBoxEdit, _e As CancelEventArgs)
+                                               ' Prüfe nur bei Änderung, nicht beim Anzeigen
+                                               If Not oItems.Contains(_sender.EditValue) AndAlso _sender.IsModified Then
+                                                   _e.Cancel = True
+                                                   _sender.ErrorText = "Ungültiger Wert - bitte neu auswählen"
+                                               End If
                                            End Sub
 
             If pDataTable IsNot Nothing Then
@@ -846,7 +861,6 @@ Public Class ClassControlCreator
             Return oEditor
         End If
     End Function
-
     Public Sub GridTables_HandleControlValueChange(pControlPanel As XtraScrollableControl, pColumnsWithSqlAndControlPlaceholders As DataTable)
         If Not IsNothing(pColumnsWithSqlAndControlPlaceholders) AndAlso pColumnsWithSqlAndControlPlaceholders.Rows.Count > 0 Then
             For Each oRow As DataRow In pColumnsWithSqlAndControlPlaceholders.Rows
diff --git a/app/TaskFlow/ControlCreator/GridControl.vb b/app/TaskFlow/ControlCreator/GridControl.vb
index 02593a9..22caaca 100644
--- a/app/TaskFlow/ControlCreator/GridControl.vb
+++ b/app/TaskFlow/ControlCreator/GridControl.vb
@@ -462,23 +462,43 @@ Namespace ControlCreator
             isApplyingInheritedValue = True
             Try
                 _Logger.Info(String.Format("Inherit Value is active for column. So inheritting the value [{0}]...", valueToApply))
-                For dataIndex As Integer = listIndex + 1 To pView.DataRowCount - 1
-                    Dim targetHandle = pView.GetRowHandle(dataIndex)
-                    If targetHandle = DevExpress.XtraGrid.GridControl.InvalidRowHandle OrElse pView.IsGroupRow(targetHandle) Then
-                        Continue For
-                    End If
 
-                    If pView.IsNewItemRow(targetHandle) Then
-                        Exit For
-                    End If
+                ' Batch-Update mit BeginUpdate/EndUpdate für bessere Performance
+                pView.BeginUpdate()
+                Try
+                    For dataIndex As Integer = listIndex + 1 To pView.DataRowCount - 1
+                        Dim targetHandle = pView.GetRowHandle(dataIndex)
+                        If targetHandle = DevExpress.XtraGrid.GridControl.InvalidRowHandle OrElse pView.IsGroupRow(targetHandle) Then
+                            Continue For
+                        End If
 
-                    Dim existingValue = pView.GetRowCellValue(targetHandle, pArgs.Column.FieldName)
-                    If Equals(existingValue, valueToApply) Then
-                        Continue For
-                    End If
+                        If pView.IsNewItemRow(targetHandle) Then
+                            Exit For
+                        End If
+
+                        Dim existingValue = pView.GetRowCellValue(targetHandle, pArgs.Column.FieldName)
+                        If Equals(existingValue, valueToApply) Then
+                            Continue For
+                        End If
+
+                        pView.SetRowCellValue(targetHandle, pArgs.Column.FieldName, valueToApply)
+                    Next
+
+                    ' WICHTIG: Nach dem Setzen der Werte die Spalte neu zeichnen
+                    pView.LayoutChanged()
+
+                    ' Nur die betroffene Spalte invalidieren (effizienter als alle Zeilen)
+                    For dataIndex As Integer = listIndex + 1 To pView.DataRowCount - 1
+                        Dim targetHandle = pView.GetRowHandle(dataIndex)
+                        If targetHandle <> DevExpress.XtraGrid.GridControl.InvalidRowHandle AndAlso Not pView.IsNewItemRow(targetHandle) Then
+                            pView.InvalidateRowCell(targetHandle, pArgs.Column)
+                        End If
+                    Next
+
+                Finally
+                    pView.EndUpdate()
+                End Try
 
-                    pView.SetRowCellValue(targetHandle, pArgs.Column.FieldName, valueToApply)
-                Next
             Finally
                 isApplyingInheritedValue = False
             End Try
diff --git a/app/TaskFlow/frmMain.resx b/app/TaskFlow/frmMain.resx
index 2a0f901..3b2bf0b 100644
--- a/app/TaskFlow/frmMain.resx
+++ b/app/TaskFlow/frmMain.resx
@@ -125,7 +125,7 @@
         AAEAAAD/////AQAAAAAAAAAMAgAAAFdTeXN0ZW0uV2luZG93cy5Gb3JtcywgVmVyc2lvbj00LjAuMC4w
         LCBDdWx0dXJlPW5ldXRyYWwsIFB1YmxpY0tleVRva2VuPWI3N2E1YzU2MTkzNGUwODkFAQAAACZTeXN0
         ZW0uV2luZG93cy5Gb3Jtcy5JbWFnZUxpc3RTdHJlYW1lcgEAAAAERGF0YQcCAgAAAAkDAAAADwMAAADw
-        CAAAAk1TRnQBSQFMAgEBAgEAAbABCwGwAQsBEAEAARABAAT/AQkBAAj/AUIBTQE2AQQGAAE2AQQCAAEo
+        CAAAAk1TRnQBSQFMAgEBAgEAAbgBCwG4AQsBEAEAARABAAT/AQkBAAj/AUIBTQE2AQQGAAE2AQQCAAEo
         AwABQAMAARADAAEBAQABCAYAAQQYAAGAAgABgAMAAoABAAGAAwABgAEAAYABAAKAAgADwAEAAcAB3AHA
         AQAB8AHKAaYBAAEzBQABMwEAATMBAAEzAQACMwIAAxYBAAMcAQADIgEAAykBAANVAQADTQEAA0IBAAM5
         AQABgAF8Af8BAAJQAf8BAAGTAQAB1gEAAf8B7AHMAQABxgHWAe8BAAHWAucBAAGQAakBrQIAAf8BMwMA