diff --git a/src/BlazorDatasheet.Core/Commands/MergeCellsCommand.cs b/src/BlazorDatasheet.Core/Commands/MergeCellsCommand.cs
index 3fccee00..2923fa70 100644
--- a/src/BlazorDatasheet.Core/Commands/MergeCellsCommand.cs
+++ b/src/BlazorDatasheet.Core/Commands/MergeCellsCommand.cs
@@ -25,6 +25,7 @@ public MergeCellsCommand(IRegion region)
 
     public bool Execute(Sheet sheet)
     {
+        sheet.Cells.BatchChanges();
         _overridenMergedRegions.Clear();
         _mergesPerformed.Clear();
 
@@ -53,16 +54,14 @@ public bool Execute(Sheet sheet)
         // Store the merge that we are doing and perform the actual merge
         _mergesPerformed.Add(region);
         sheet.Cells.MergeImpl(region);
+        sheet.Cells.EndBatchChanges();
         return true;
     }
 
-    private CellValueChange getValueChangeOnClear(int row, int col, Sheet sheet)
-    {
-        return new CellValueChange(row, col, sheet.Cells.GetValue(row, col));
-    }
-
     public bool Undo(Sheet sheet)
     {
+        sheet.Cells.BatchChanges();
+        
         // Undo the merge we performed
         foreach (var merge in _mergesPerformed)
             sheet.Cells.UnMergeCellsImpl(merge);
@@ -72,6 +71,7 @@ public bool Undo(Sheet sheet)
 
         // Restore all the cell values that were lost when merging
         sheet.Cells.Restore(_restoreData);
+        sheet.Cells.EndBatchChanges();
 
         return true;
     }
diff --git a/src/BlazorDatasheet.Core/Data/Cells/CellStore.cs b/src/BlazorDatasheet.Core/Data/Cells/CellStore.cs
index f4edae52..c22b248f 100644
--- a/src/BlazorDatasheet.Core/Data/Cells/CellStore.cs
+++ b/src/BlazorDatasheet.Core/Data/Cells/CellStore.cs
@@ -174,6 +174,7 @@ internal CellStoreRestoreData CopyImpl(IRegion fromRegion, IRegion toRegion, Cop
         {
             restoreData.ValueRestoreData = _dataStore.Copy(fromRegion, toRegion);
             restoreData.ValidRestoreData = _validStore.Copy(fromRegion, toRegion);
+            restoreData.FormulaRestoreData = _formulaStore.Clear(toRegion);
         }
 
         if (options.CopyFormula)
diff --git a/src/BlazorDatasheet.Core/FormulaEngine/FormulaEngine.cs b/src/BlazorDatasheet.Core/FormulaEngine/FormulaEngine.cs
index 0b83b475..cdfa0a85 100644
--- a/src/BlazorDatasheet.Core/FormulaEngine/FormulaEngine.cs
+++ b/src/BlazorDatasheet.Core/FormulaEngine/FormulaEngine.cs
@@ -2,6 +2,7 @@
 using BlazorDatasheet.Core.Data.Cells;
 using BlazorDatasheet.Core.Events;
 using BlazorDatasheet.Core.Events.Edit;
+using BlazorDatasheet.Core.Events.Layout;
 using BlazorDatasheet.DataStructures.Geometry;
 using BlazorDatasheet.DataStructures.Graph;
 using BlazorDatasheet.DataStructures.References;
@@ -29,7 +30,7 @@ public class FormulaEngine
     /// This should ideally keep track of the formula that reference the range also,
     /// but for now it's just whether it's referenced or not.
     /// </summary>
-    private RegionDataStore<bool> _observedRanges = new();
+    private readonly RegionDataStore<bool> _observedRanges;
 
     public bool IsCalculating { get; private set; }
 
@@ -43,6 +44,7 @@ public FormulaEngine(Sheet sheet)
         _environment = new SheetEnvironment(sheet);
         _evaluator = new Evaluator(_environment);
         _dependencyGraph = new DependencyGraph();
+        _observedRanges = new RegionDataStore<bool>();
 
         RegisterDefaultFunctions();
     }
diff --git a/src/BlazorDatasheet/Datasheet.razor b/src/BlazorDatasheet/Datasheet.razor
index f01c82ce..a4d5d3b8 100644
--- a/src/BlazorDatasheet/Datasheet.razor
+++ b/src/BlazorDatasheet/Datasheet.razor
@@ -122,12 +122,16 @@
                         var mergesInView = Sheet.Cells.GetMerges(this.Viewport.VisibleRegion);
                         @foreach (var merge in mergesInView)
                         {
-                            var row = merge.Top;
-                            var col = merge.Left;
+                            var constrainedMerge = merge.GetIntersection(_sheetLocal.Region);
+                            if (constrainedMerge == null)
+                                continue;
+
+                            var row = constrainedMerge.Top;
+                            var col = constrainedMerge.Left;
                             var cell = _visualSheet.GetVisualCell(row, col);
 
                             <div id="merge"
-                                 style="@GetAbsoluteCellPositionStyles(row, col, merge.Height, merge.Width)"
+                                 style="@GetAbsoluteCellPositionStyles(row, col, constrainedMerge.Height, constrainedMerge.Width)"
                                  class="sheet-cell"
                                  @onmouseup="e => HandleCellMouseUp(row, col, e.MetaKey, e.CtrlKey, e.ShiftKey)"
                                  @ondblclick="e => HandleCellDoubleClick(row, col, e.MetaKey, e.CtrlKey, e.ShiftKey)"
diff --git a/src/BlazorDatasheet/Edit/EditorOverlayRenderer.razor b/src/BlazorDatasheet/Edit/EditorOverlayRenderer.razor
index da181ce4..7cb2e5b2 100644
--- a/src/BlazorDatasheet/Edit/EditorOverlayRenderer.razor
+++ b/src/BlazorDatasheet/Edit/EditorOverlayRenderer.razor
@@ -23,19 +23,15 @@
 
 @code {
 
-    [Parameter, EditorRequired]
-    public Sheet Sheet { get; set; }
+    [Parameter, EditorRequired] public Sheet Sheet { get; set; }
 
-    [Parameter, EditorRequired]
-    public Dictionary<string, CellTypeDefinition> CustomCellTypes { get; set; }
+    [Parameter, EditorRequired] public Dictionary<string, CellTypeDefinition> CustomCellTypes { get; set; }
 
-    [Parameter, EditorRequired]
-    public Dictionary<string, CellTypeDefinition> DefaultCellTypes { get; set; }
+    [Parameter, EditorRequired] public Dictionary<string, CellTypeDefinition> DefaultCellTypes { get; set; }
 
     private Sheet? _sheet;
 
-    [Parameter, EditorRequired]
-    public CellLayoutProvider CellLayoutProvider { get; set; }
+    [Parameter, EditorRequired] public CellLayoutProvider CellLayoutProvider { get; set; }
 
     /// The type of the active editor, which is an ICellEditor
     private Type? ActiveEditorType { get; set; } = typeof(TextEditorComponent);
@@ -75,11 +71,13 @@
                 _sheet.Editor.EditFinished -= EditorOnEditFinished;
                 _sheet.Editor.EditValueChanged -= EditorOnEditValueChanged;
             }
+
             _sheet = Sheet;
             _sheet.Editor.EditBegin += EditorOnEditBegin;
             _sheet.Editor.EditFinished += EditorOnEditFinished;
             _sheet.Editor.EditValueChanged += EditorOnEditValueChanged;
         }
+
         base.OnParametersSet();
     }
 
@@ -138,9 +136,9 @@
             {
                 if (!EqualityComparer<ElementReference>.Default.Equals(_activeCellEditor.InputRef, default(ElementReference)))
                 {
-    // Request focus with a delay so that it the field doesn't capture any oninput events
-    // from the text field that is just rendered. If not, there's inconsistent behaviour between
-    // WASM and Server.
+                    // Request focus with a delay so that it the field doesn't capture any oninput events
+                    // from the text field that is just rendered. If not, there's inconsistent behaviour between
+                    // WASM and Server.
                     await JS.InvokeVoidAsync("setFocusWithTimeout", _activeCellEditor.InputRef, 0);
                 }
             }
@@ -190,7 +188,9 @@
         var left = CellLayoutProvider.ComputeLeftPosition(EditCell.Col);
         var top = CellLayoutProvider.ComputeTopPosition(EditCell.Row);
 
-        var mergedPosn = Sheet.Cells.GetMerge(EditCell.Row, EditCell.Col);
+        var mergedPosn = Sheet.Cells.GetMerge(EditCell.Row, EditCell.Col)?
+            .GetIntersection(Sheet.Region);
+        
         int colSpan = 1;
         int rowSpan = 1;