MF455dw Suddenly printing on both side of paper even though settings indicates 2 sided printing off

[DarrylB]

Why is this happening? 

[Hector]

Hello DarrylIB,

The issue could be caused by settings applied in the program that you are printing from or by settings in the printer driver. We would be happy to assist with the issue. To provide some feedback or some troubleshooting steps, we would need some additional information. If you could reply to this message with the information below, we can provide some assistance.

1. What version of the Mac or Windows operating system are you using on your computer?
2. What program are you printing from?

[DarrylB]

I changed it in print settings and it's fine now, but I never changed it to begin with so I don't know how it changed itself. I'm using Windows in on a Mac.