We found a bug in the com.vaadin.addon.tableexport.ExcelExport. If you have more than 2 levels in your Excel spreadsheet, the recursive method calls do not properly track row numbers so you get rows with missing data rows with the wrong data. Is this an appropriate place to report a bug?
It might be a good idea to file a ticket in the issue tracker:
https://code.google.com/p/tableexport-for-vaadin/issues/list
https://vaadin.com/directory#addon/tableexport:vaadin