I tried placing a plain button inside a column and I got this error. Any ideas on what caused it? I’m not working with any data, just the layout of the page. Something went wrong in Mendix Studio Pro. Index must be within the bounds of the List. (Parameter 'index') System.ArgumentOutOfRangeException: Index must be within the bounds of the List. (Parameter 'index') at System.Collections.Generic.List`1.Insert(Int32 index, T item) at Mendix.Modeler.Utility.ListWrapper`2.Insert(Int32 index, T item) in C:\Users\Autobuild\workspace\AppStudio4.0-Build\modeler\Mendix.Modeler.Utility\Collections\List\ListWrapper.cs:line 78 at Mendix.Modeler.Utility.UndoAwareList`1.Insert(Int32 index, T item) in C:\Users\Autobuild\workspace\AppStudio4.0-Build\modeler\Mendix.Modeler.Utility\Undo\UndoAwareList.cs:line 67 at Mendix.Modeler.WebUI.Forms.Common.ElementUtil.InsertChild[T](IFormsElementContainer container, IList`1 list, Int32 index, T subject, Boolean fix) in C:\Users\Autobuild\workspace\AppStudio4.0-Build\modeler\Mendix.Modeler.WebUI\Forms\Common\ElementUtil.cs:line 73 at Mendix.Modeler.WebUI.View.Editors.DesignMode.DesignModeEditor.InsertWidget(IFormsElementContainer container, String propertyName, Int32 index, Widget subject) in C:\Users\Autobuild\workspace\AppStudio4.0-Build\modeler\Mendix.Modeler.WebUI.View\Editors\DesignMode\DesignModeEditor.cs:line 0 at Mendix.Modeler.WebUI.View.Editors.DesignMode.DesignModeEditor.<>c__DisplayClass64_1.<OnElementDragDrop>b__1() in C:\Users\Autobuild\workspace\AppStudio4.0-Build\modeler\Mendix.Modeler.WebUI.View\Editors\DesignMode\DesignModeEditor.cs:line 498 at Mendix.Modeler.WebUI.View.Views.DropZones.DropZoneUtil.<>c__DisplayClass0_0.<InsertElement>b__0() in C:\Users\Autobuild\workspace\AppStudio4.0-Build\modeler\Mendix.Modeler.WebUI.View\Views\DropZones\DropZoneUtil.cs:line 14 at Mendix.Modeler.Utility.UndoManager.TransactionDo(IUndoManagerProvider provider, String actionDescription, Func`1 action) in C:\Users\Autobuild\workspace\AppStudio4.0-Build\modeler\Mendix.Modeler.Utility\Undo\UndoManager.cs:line 280 at Mendix.Modeler.WebUI.View.Views.DropZones.DropZoneUtil.InsertElement(IMoveableView view, IUndoManagerProvider provider, Action setElement) in C:\Users\Autobuild\workspace\AppStudio4.0-Build\modeler\Mendix.Modeler.WebUI.View\Views\DropZones\DropZoneUtil.cs:line 16 at Mendix.Modeler.WebUI.View.Editors.DesignMode.DesignModeEditor.<>c__DisplayClass64_0.<OnElementDragDrop>b__0() in C:\Users\Autobuild\workspace\AppStudio4.0-Build\modeler\Mendix.Modeler.WebUI.View\Editors\DesignMode\DesignModeEditor.cs:line 499 at Mendix.Modeler.Utility.UndoManager.<>c__DisplayClass43_0.<Do>b__0() in C:\Users\Autobuild\workspace\AppStudio4.0-Build\modeler\Mendix.Modeler.Utility\Undo\UndoManager.cs:line 136 at Mendix.Modeler.Utility.UndoManager.TransactionDo(IUndoManagerProvider provider, String actionDescription, Func`1 action) in C:\Users\Autobuild\workspace\AppStudio4.0-Build\modeler\Mendix.Modeler.Utility\Undo\UndoManager.cs:line 280 at Mendix.Modeler.WebUI.View.Editors.DesignMode.DesignModeEditor.OnElementDragDrop(Guid guid, String propertyName, Int32 index) in C:\Users\Autobuild\workspace\AppStudio4.0-Build\modeler\Mendix.Modeler.WebUI.View\Editors\DesignMode\DesignModeEditor.cs:line 501 at Mendix.Modeler.WebUI.View.Editors.DesignMode.DesignModeEditor.OnBrowserMessage(String message, Object data) in C:\Users\Autobuild\workspace\AppStudio4.0-Build\modeler\Mendix.Modeler.WebUI.View\Editors\DesignMode\DesignModeEditor.cs:line 429 at Mendix.Modeler.WebEditors.WebEditor.<>c__DisplayClass35_0.<OnMessageReceived>b__0() in C:\Users\Autobuild\workspace\AppStudio4.0-Build\modeler\Mendix.Modeler.WebEditors\WebEditor.cs:line 129