I have the same problem. My website uses Brazilian date format. DD/MM/YYYY
But, download manager always tries to order by date using US format MM/DD/YYYY.
This causes a problem. For example, 07/01/2018 is showed as newer than 04/11/2018.
This needs to be fixed. Eventhough my website is set to pt-BR and has BR date format, WPDM is not considering the correct format.
Only happens with responsive table mode.