I don't know what it could be. Banding doesn't usually have an exact pattern like this. I really wish uploading it didn't change what I am seeing on my screen. The lines are perfectly straight, perfectly spaced horizontally and verically and the colors are evenly gray almost like a screen was placed on top of that area of the photo and only appears after the crop. As soon as I undo the crop and just zoom in, it is not there. It might be on other areas of the photo but not as noticable due to the colors.