To reproduce:
-add RadRotator
-add items to the rotator: add 3 RadLabels
-enable Running property
-run the project and you will see that initially all RadLabels are visible and they overlap each other. After all items are rotated once, the layout is correct

Workaround:
public Form1()
{
    InitializeComponent();

    this.radRotator1.Running = true;
    foreach (RadItem item in this.radRotator1.Items)
    {
        item.Visibility = ElementVisibility.Collapsed;
    } 
}

If you have a RadRotator with several RadImageButtonElement and you try to go to the next imagebuttons quickly (by calling Next() several times), you end with an empty RadRotator.

Workaround: 
  DateTime dt = DateTime.Now;
        int interval = 500;

        private void radButton1_Click(object sender, EventArgs e)
        {
            TimeSpan span = DateTime.Now - dt;
            if (span.TotalMilliseconds > interval)
            {
                this.radRotator1.Next();
                dt = DateTime.Now;
            }
        }

        private void radButton2_Click(object sender, EventArgs e)
        {
            TimeSpan span = DateTime.Now - dt;
            if (span.TotalMilliseconds > interval)
            {
                this.radRotator1.Previous();
                dt = DateTime.Now;
            }
        }