Slightly too long "A4"'s end up with big black part in page

[Jan Vlug]

For some reason some organisations send me letters that are slightly (~4 mm) longer than A4. When I scan these documents from my feeder, they end up on way too long pages, where the part that is not scanned is black. The size of the resulting pages when saved to pdf is: 8.27 × 15.82 inch.
Even when I set the page size to A4 in the preferences, this still happens. The only work around that I found is scanning directly from the glass plate (so not using the sheet feeder) but this takes a lot of extra time.
The printer I'm using is: HP_officejet_4650_series.
I tested this also with xsane. xsane does not produce the black area. But it prints something along the lines as: gray area detected.
Debug log is attached.

[Jan Vlug (jan-vlug)]

I reported this also here: https://bugzilla.gnome.org/show_bug.cgi?id=782787
I will further provide updates and attachments in the GNOME Bugzilla issue mentioned above.