In the Track Change mode, try to insert several images using standard InsertPictureCommand (or even Editor.InsertImage()) double enter and then again. Or insert text between already inserted images.

The error could be also observed when accepting all changes.

• Each RichText element should contain a unique id. The id contains DateTime.UtcNow.Ticks. This format is requiring to know which RT elements were added from the last change.
• Export these ids into html as is and import.
• For compatibility, id should have a different attribute name, for example:
  

  <p data-telerik-id="Paragraph637567542110611335">
  	<span data-telerik-id="Span637567542110611345">
  		Test
  	</span>
  </p>

  Note: data-* is Global attribute name: https://www.w3schools.com/tags/att_data-.asp
  
  Id value example:
  

  public class HiResDateTime
  {
  	private static long lastTimeStamp = DateTime.UtcNow.Ticks;
  	private static readonly Regex digitsOnly = new Regex(@"[^\d]");
  	public static long UtcNowTicks
  	{
  		get
  		{
  			long original, newValue;
  			do
  			{
  				original = lastTimeStamp;
  				long now = DateTime.UtcNow.Ticks;
  				newValue = Math.Max(now, original + 1);
  			} while (Interlocked.CompareExchange
  						 (ref lastTimeStamp, newValue, original) != original);
  
  			return newValue;
  		}
  	}
  
  	public static string UtcNowTicksString => digitsOnly.Replace(UtcNowTicks.ToString(), "");
  }

  
  

The pasted content is not formatted properly, resulting in an InvalidOperationException("'Token EndElement in state EndRootElement would result in an invalid XML document. Make sure that the ConformanceLevel setting is set to ConformanceLevel.Fragment or ConformanceLevel.Auto if you want to write an XML fragment. ') when saving the content to DOCX.

Steps to reproduce:

• Create a document
• Activate Review/Change Tracking
• Create a table in a separate MS Word file and add some text at least in the first cell
• Copy from MS Word and paste it as the first element in the document
• Save the document as an MS Word document
  

Workaround: intercept the table paste and add an empty paragraph as the first element of the document before the table.

Another case:

• Create a new document
• Be sure that Change Tracking is deactivated
• Create a table in a separate MS Word file and add some text at least in the first cell
• Copy from MS Word and paste it as the first element in the document
• Activate Review/Change Tracking
• Just after the first table, paste the table again: the second table seems to be merged with the first table, with no paragraph in between, but with the vertical line in the margin showing that the second table has change tracking
• Save the document as a MS Word document

Steps to reproduce: 

• In MS Word, create a table with text in every cell
• In the RadRichTextBox, create a new document
• Activate Review/Track Changes
• Copy and paste the table from MS Word: only the first cell has change tracking markup
• Insert a paragraph after the first table and paste the table again: now, none of the cells has change tracking markup

Currently, there is a DocumentHistory property IsEnabled indicating whether the history for the RadDocument is enabled. This property is not working and history cannot be disabled.

Workaround:

Use DocumentHistory Clear() method by attaching to editor's CommandExecuted event.

        private void Editor_CommandExecuted(object sender, Telerik.Windows.Documents.RichTextBoxCommands.CommandExecutedEventArgs e)
        {
            editor.Document.History.Clear();
        }

When the Track Changes is On and we try to change the style it applies the first time but the second try throws an exception and the style doesn't apply: System.ArgumentNullException: 'Value cannot be null. Parameter name: owner'.

1. Add new text "TEST".
2. Select the text and set a new style "Heading 2", then "Heading 1".
Observed: Heading 1 doesn`t appear.

When the Track Changes is activated, a Hyperlink is inserted to a text and we try to reject changes the rejection is not applied correctly.

The result: