When you click for second time the caret locates in the correct position. I.e. there are needed 2 clicks before first line of paragraph which starts with bookmark to set the correct caret position. It also cause the problem of incorrect selection which will select the previous paragraph.

This is because bookmarks essentially don't have position before them.

RadRichTextBox: Add import/export in the following formats: .mht .odt .epub .doc

In some languages such as German and Swedish, combining correct words into one is a common morphological pattern. Compound words not included in the dictionaries should not be marked as misspelled.

The spellchecker does not recognize words with non-breaking spaces between them as separate.
A workaround when pasting text into the RadRichTextBox is to subscribe to the CommandExecuting event of the control, get the paste text from the clipboard and replace all non-brekaing spaces with spaces.

private void editor_CommandExecuting(object sender, Telerik.Windows.Documents.RichTextBoxCommands.CommandExecutingEventArgs e)
        {
            if (e.Command is PasteCommand)
            {
                var pasteText = Clipboard.GetDataObject().GetData("HTML Format") as string;
                if (pasteText != null)
                {
                    pasteText=  pasteText.Replace("&nbsp", " ").Replace(' ',' ');
                    var originalDataObject = Clipboard.GetDataObject();
                    DataObject dataObject = new DataObject();
                    foreach (string format in originalDataObject.GetFormats())
                    {
                        dataObject.SetData(format, originalDataObject.GetData(format));
                    }
                    dataObject.SetData("HTML Format", pasteText);
                    Clipboard.SetDataObject(dataObject);
                }               
            }
        }