Use the following code:

RadCarousel c = new RadCarousel
{
    Parent = this,
    Dock = DockStyle.Fill
};

for (int i = 0; i < 50; i++)
{
    c.Items.Add(new MyButtonElement("Button " + i));
}

c.VisibleItemCount = 3;

Start the application and click the buttons to switch the elements, you will see the exception