Content faded partway down page

Printing PDF documents from Ubuntu on our HP LaserJet P4515n only works partially on pages. The top part looks fine, but partway down the text suddenly changes to being faded out — still there, but in a much lighter (unreadable) shade of grey, a bit like when ink is running out on an inkjet printer. Sometimes this can even be partway through a line, meaning the top part of characters are readable and bottom not.

This only happens when printing from Linux. The same PDF documents when printed from Windows come out just fine.

We're using Cups on Ubuntu 16.04.3 with the hplip package installed. The driver is listed as:

   HP LaserJet p4515n, hpcups 3.16.3 (color, 2-sided printing)

[though it does neither colour nor two-sided printing], and the connection as:

  hp:/net/HP_LaserJet_P4515?ip=192.168.<etc>

What can we do to have all of pages print on Linux, just as they do on WIndows? THanks.