In a touch scenario, when there are RadComboBox instances one below the other, selecting an item from a RadComboBox opens the RadComboBox instance, which is below the selected item. 

This is present when there is a global Style that targets the native WPF ScrollViewer element, which sets its PanningMode property to Both. 

To work this around, set the TouchManager.TouchMode to HitTestHidden, in order to exclude the RadComboBox from the TouchManager's events propagation.