Kibo informs me that (Rowan Crowe) stated
that:

Is this normal? It shows in areas where there is a fair amount of one
colour, like sky. I'm hoping it's a normal quirk of the sensor rather
than something more serious like a half dead multiplexing transistor.

Here's a sample 1:1 crop of some sky, it's not the best example but
hopefully the lines are apparent.

http://media.sensationcontent.com/ro...ntal-lines.tif

The only faults I can see in that crop are lots of fine (5-10 pixel)
compression artifacts, that look a bit like lots of tiny scratches. If
that's what you're talking about, the problem is that you're
over-compressing your images. If you're shooting JPEGs (rather than
RAW), you should check the image quality settings you're using in both
the camera & whatever software you're using to process your photos.

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------