When a table is copied (without a paragraph before it) and pasted as first element in a Section in RadRichTextBox with Track Changes enabled, accepting all changes throws (handled) InvalidCastException. Changes are not accepted.

Workaround: Attach to RadRichTextBox.CommandExecuting event, and add paragraph before the table in the document fragment in the clipboard.
private void RadRichTextBox_CommandExecuting(object sender, Telerik.Windows.Documents.RichTextBoxCommands.CommandExecutingEventArgs e)
{
    if (e.Command is Telerik.Windows.Documents.RichTextBoxCommands.PasteCommand)
    {
        if (this.radRichTextBox.Document.IsTrackChangesEnabled)
        {
            DocumentFragment documentFromClipboard = ClipboardEx.GetDocument();
 
            if (documentFromClipboard != null)
            {
                e.Cancel = true;
 
                RadDocument documentFormClipboard = documentFromClipboard.ToDocument();
 
                if (documentFormClipboard.EnumerateChildrenOfType<Table>().Count() > 0)
                {
                    Section firstSection = documentFormClipboard.Sections.FirstOrDefault();
                    if (firstSection.EnumerateChildrenOfType<Table>().Count() > 0)
                    {
                        if (firstSection.EnumerateChildrenOfType<Table>().FirstOrDefault() != null)
                        {
                            Table table = firstSection.EnumerateChildrenOfType<Table>().FirstOrDefault();
                            Paragraph paragraph = new Paragraph() { SpacingAfter = 0, SpacingBefore = 0, LineSpacing = 0, FontSize = 1 };
                            firstSection.Blocks.AddBefore(table, paragraph);
 
                            RadDocumentEditor editor = new RadDocumentEditor(this.radRichTextBox.Document);
                            DocumentFragment fragment = new DocumentFragment(documentFormClipboard);
                            editor.InsertFragment(fragment);
                        }
                    }
                }
            }
        }
    }
}