When a table in HTML document has width set to 0 (through an attribute or CSS style),  the table is imported with 0 width in the document model. This makes the content unreadable. 

Instead, such width should be treated as if width is not set at all - this way the layout will use only the widths set to the cells.

Workaround: Clear the PreferredWidth property if it is 0.
var tables = this.radRichTextBox.Document.EnumerateChildrenOfType<Table>();
foreach (var table in tables)
{
    if (table.PreferredWidth.Value == 0)
    {
        table.PreferredWidth = null;
    }
}

Fix available in LIB Version 2018.1.326.