It looks to me like a thumbnail of you 1280×960 image was used somewhere in the process. It’s displayed as 960×260, but has 4×4 pixelation. That suggests something squeezed it to 240×65 then re-expanded it.
So do as thesacredpath suggests. Make a crop of your 1280×960 to a size of 960×260 directly. If that crop sizing isn’t the view you want, make a resized copy of the original 1280×960 and try to crop that to 960×260.