The bottom of the card that shows the validation summary is missing (overlapped by the summary visual) when the Expression_Dark theme is used.

To work this around, you can set the Margin of the DataFormValidationSummary element to 0, via an implicit style defined in the RadCardView.Resources dictionary.

<telerik:RadCardView.Resources>
    <Style TargetType="dataForm:DataFormValidationSummary">
        <Setter Property="Margin" Value="0" />
    </Style>
</telerik:RadCardView.Resources>

If the CardView control is focused and the Enter key is pressed NullReferenceException appears. 

To resolve this use ICollectionView (like QueryableCollectionView) as the ItemsSource of the control.

Removing an item from the ItemsSource always removes the last card in the UI, regardless of the item's index in the ItemsSource. For example, if you remove an item at index 0, the last visual element (card) will be removed instead of the first one in the view. 

To resolve the issue, you can reset the ItemsSource of the RadCardView control after the collection changed action.

var source = this.cardView.ItemsSource;
this.cardView.ItemsSource = null;
this.cardView.ItemsSource = source;