How do I fix this problem?
If your duplex (double-sided / two-sided) prints are printing upside-down (or 'short-edge' when you're expecting 'long-edge'), then you will need to set the 'Duplex (long-edge) back-sheet treatment' under Edit printer to 'Rotate'.
Duplex dropdown option set to rotate within a printer's settings.
Note: You may experience this issue on low-end printers, such as the Canon MX922.