hp-scan lacks "long/short side" duplex option: even pages are scanned upside down with duplex

I can confirm this behaviour and I described the same issue with a HP Officejet x476dw in an earlier launchpad question:

https://answers.launchpad.net/hplip/+question/280962

My bug report is from 2014 and we're in 2016 now: I fear nobody is ever going to fix it.

Please fix this in the scanner backend so that also sane-based programs will benefit. FWIW, scanning from the device (in my case a X476dw) yields PDFs with all pages upright. So obviously the hardware/firmware can scan properly.

I doubt that HP puts enough ressources onto hplip to get bugs as this fixed in a proper timeframe. If you take a look at the launchpad project you can see that they have >1K new open undecided bug reports. The only person from HP who seems to comment on bug reports is https://launchpad.net/~goutam-hplip and he currently has 16 bugs open. Most of the time he posts "fixed upstream" updates so i guess this lp project is more of a general unsorted bug list than a real bug tracker.

The good news on the other hand is that the X476dw in contrast to its predeccessors has an open source scanning plugin (http://hplipopensource.com/hplip-web/plugin.html) that - theoretically - could be fixed by others as well. Since HP does exactly no community building here, i wonder though if any people from outside of HP know the source code enough to contribute to this?

I am experiencing the same issue using HPLIP 3.20.6 on Ubuntu 18.04 and 3.18.3 on Ubuntu 16.04 with an OfficeJet Pro 8620. The "even" pages are not only upside down but frequently have a black rectangle appended to the A4 scanning area. The problem occurs with all the scanning programs I have tried, including Gnome simple-scan (the default Ubuntu program).