Hello,
In PB2017R3 when you do dw.SaveAs XLSX! an there is a cell with more than 32767 characters (character size limit of Ecel's cell) - resulting .xlsx file will consider this cell unreadable in MicroSoft Excel. At the same time Open Office just truncate extra characters. This is what you get when open such .xlsx file in MS Excel:
Thanks,
Aliaksei.