Aspose.Word 1.1 does not recognize nested tables (tables inside of tables).
No error is thrown, just output text contains one table, no nested table. Text is not lost, but nested table structure is lost during mail merge operation.
Arrange your table to be a single table without nested tables. This is easily done in Word, just insert, merge and split cells until you are happy. Apply formatting and borders as you want. You can also switch into “Draw Table” mode in Word to simplify arranging cells.
Native support for nested tables will be included in future versions of Aspose.Word.