Having two mention providers and using the second right after using the first one actually loads the source of the first provider.

Some dialogs like ParagraphPropertiesDialog and SectionColumnsDialog have dependency properties for defining the width of the numerics. When creating implicit style, the value of these custom properties results in 0 and they are invisible in the UI.

Workaround: Set the value of the property in the custom style. For paragraph properties dialog:

<Style TargetType="rtb:RadParagraphPropertiesDialog" BasedOn="{StaticResource CustomStyle}" >
    <Setter Property="NumericWidth" Value="85"/>
</Style>

1. In MS Word, create a table with text in every cell, but just before the table, add a paragraph with text (you cannot reproduce the problem with an empty paragraph)
2. In the RadRichTextBox, create a new document
3. Activate Review/Track Changes
4. Copy and paste all the content from MS Word >> as a result none of the cells in the table has change tracking markup
5. If you copy only the table from MS Word (without the non-empty paragraph), it is working as expected

Exception when importing a document with an empty table.

Workaround: Remove the empty tables:

DocxFormatProvider provider = new DocxFormatProvider();
var doc = provider.Import(File.ReadAllBytes(@"C:\Users\mpc\Downloads\22-51.docx"));

foreach (var section in doc.Sections)
{
    var tables = section.EnumerateChildrenOfType<Table>();
    foreach (var table in tables.ToList())
    {
        if (table.Rows.Count == 0)
        {
            section.Blocks.Remove(table);
        }
    }
}
radRichTextBox.Document = doc;

No visual cue when image deleted or inserted when "Track changes" is activated. 

When inserting an image with the Track Changes option toggled, the image should be underlined with red and it isn't. When deleting an image with Track Changes on, it is also not crossed with red. In both cases, the only mark that a change was made is the vertical line on the left.