I have already looked at that link and tried all the things I can try at home, aside from replacing the print heads. Nothing works. The magenta seems to be the biggest offender. When I print photos that have a lot of magenta in them, I also get the horizontal lines, so it is not just the regular paper used by the printer's quality report (my first suspicion, sadly proven wrong).
I see now that this printer also cuts off the image when printing a borderless photo. I have not found a solution for that yet, either. It also went crazy in the middle of a print job (told me that I needed to power it off, lost its wireless connection, regained its connection, but would not talk to the computer). I had to turn it off and on again to reset it, and after that it seemed to print, at least.
This printer has been a very expensive mistake, considering the ink and paper I have gone through in the past week. I have four days to decide if I want to return it and just eat the cost of the ink cartridges. I am seriously considering it at this point, but will try to work things out for another day or two.