Yeah, itās really subtle. Hereās a zoom-in of your pic with the brightness and contrast increased:
Ideally, they should all look like the first dark line. That is, one dark line in the middle with equally lighter lines above and below. Skip down 3 scanlines and itās just 2 mid-gray lines next to each other. Skip down a couple more and weāre back to normal. Rinse/repeat all the way down the screen.
Itās an effect caused by the averaging of the pixels into an uneven integer multiple (that is, 4.5x at 1080p). The remainder comes out as uneven gradients.
EDIT: hereās the same image with the green-tinted lines taken out to make it easier to see the effect: