Save as XLSX fails on dates in 12.5

I have several datawindows, when we do save as XLSX those dw's without any dates work perfect

DW's with datetime data type fail. I'm on windows 7. I assumed these date (region) setting had been resolved long ago.

When we use the EXCEL8! all dw's export just fine. Its now only the new format and dates.

Can someone help out with a solution. We have tried several date formats

Thanks,

Richard