HP 9015e: White lines across photo or any solid image in "copy in Black" only

[snowtrains-78]

Bought an HP OficeJet 9015e from Amazon Prime. During the first week while checking out all the features I discovered that when copying a document that had some solid images in Black mode only, I got white horizontal lines every 1-1/4" down the copied sheet. It did not do this in Color mode. It did not do this printing the same image from a scan in PDF in either color or grayscale. The problem is only when copying in Black on the flat bed or ADF which does not go through the computer or wifi. I called Amazon and they put me in touch with an HP Tech. He stepped me thru several tests and confirmed the above problem and said it must be a hardware issue unrelated to the cartridges or printhead. So, HP shipped me a replacement 9015e but to use the cartridges and printhead from the original unit.  Guess what: the new one does the same thing. Please note that this only occurs in the "Copy in Black" mode from the unit. What is the real solution for this problem or is it a design issue?

[Valsimot]

The black copy is a draft mostly for text copying to save ink, those lines you see in photos are not visible on the text. 

[snowtrains-78]

I noticed that it didn't seem to affect text, just the solid parts of images on a page. (I was only trying to save on ink). Any how I tend to believe it is an inherent flaw in that model since the hp replacement unit did the same thing. I went to Office Max store and tried the same thing on an HP 9125e (newer similar model) demo unit, and it copied and printed in Black without the lines.