Type a few lines in RadRichTextBox.
Double-clicking within a word, holding down the mouse button on the second click, and then drag it. 

Actual: Dragging will move the word instead of extending the selection as it should.
Expected: The selection should be extended. Moving the word shouldn't happen unless you release after the double click and then click and drag. 

The GetSupportedExtensions method of DocumentFormatProvidersManager throws NullReferenceException when invoked.

Workaround:

HashSet<string> supportedExtensions = new HashSet<string>();
foreach (var provider in DocumentFormatProvidersManager.FormatProviders)
{
    foreach (var extension in provider.SupportedExtensions)
    {
        supportedExtensions.Add(extension);
    }
}

Bookmarks are not imported and missing from a specific document scenario.

Workaround: Import and then export the document using the WordsProcessing library and then open it with the editor.

When inserting a content control (structured document tag) into an empty RadDocument using one of the overloads of the InsertStructuredDocumentTag method accessible from RadRichTextBox and RadDocumentEditor, a NullReferenceException is thrown.

Workaround: Invoke the EnsureDocumentMeasuredAndArranged method before inserting the content control:

document.EnsureDocumentMeasuredAndArranged();

RadDocumentEditor editor = new RadDocumentEditor(document);
editor.InsertStructuredDocumentTag(SdtType.CheckBox);

When the unit type is set to an inch:

Expected: to could be able to place the RulerThumb on every 1/16 of an inch.
Actual: be able to place the RulerThumb to every 1/8 of an inch. 

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:

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.

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();
        }