When I try to print double-sided documents the second page is upside-down, regardless of the app. I've searched the forums and found similar issues with solutions that either a) don't work or b) the referenced function doesn't exist. For example, deleting the printer from "Printers & Scanners" and re-adding it as an Airprint doesn't solve the problem. There doesn't seem to be a "Duplex" functions anywhere in the software.
Any help will be much appreciated. I'm using an Officejet Pro 6978 via Ethernet on a Mac running MacOS 10.13.6. Also have the latest HP printer software and firmware installed.