Video Card or Photoshop Bug? (graphics drawing glitch)

Notice the glitch at center cutting through the siemens star pattern? It goes away with the GPU disabled. I even swapped displays to rule that out.

It is sensitive to image size and doesn’t always appear, but the same Siemens star scaled to various sizes will frequently show it. Scrolling has no effect, showing that the bug cannot be in the image data itself.

On the Mac Pro with 2560 X 1600 display, the glitch is always at 800 pixels, exactly half of the 1600 screen height. And shows up in Photoshop CC full screen mode with menu bar; I am not able to reproduce in full screen mode without menu bar or with regular window.

Crop below is actual pixels.

Drawing glitch : 2013 Mac Pro, Adobe Photoshop CC 14.2.1
(actual pixels)

Similar issues are seen on the late 2013 MacBook Pro with Retina display, but the issue arises in about 1/3 down from top.

That it happens on two different Macs with two different graphics cards suggests a Photoshop bug or some kind of more general GPU bug.

Drawing glitch: late 2013 MacBook Pro, Adobe Photoshop CC 14.2.1
(actual pixels)

Glitch be gone:

GPU disabled in Photoshop CC