The MatchAllTerms search mode doesn't behave as epxected when the GroupRenderMode property of RadGridView is set to Flat.
To work this around, set the GroupRenderMode property of RadGridView to True.
When using INotifyDataErrorInfo, items are still validated even when the ValidationType property is None.
Please note that when the AutoGeneratedColumns property is set to true, the item's HasErrors property will be evaluated, but only once.
If the DisplayIndex of the columns is set when they are initialized, ColumnGroups are not displayed.
As a workaround, you can set the DisplayIndex after the columns are initialized.
The issue reproduces in the following situation.
To work this around set the SelectionUnit property of RadGridView to FullRow or use a collection type like ObservableCollection<T> instead of a DataTable.