Assuming you are sending a fax with the print driver to a Xerox MFP, I'd start with installing a Xerox V3 driver and getting rid of the Microsoft V4/Class driver you have now.
Windows 10 machine can print no problems. When Fax is selected, Windows 10 just prints the document instead of fax. MacBook on the other hands works like a champ. I'm completely stumped at this point. Where can I start.