Sisyphus it doesn't occur when I export using Node-Webkit.
Also, the sprite is a square with 1 colour. I can't understand how or why this would happen in terms of pixels and ramifications of reshaping it.
I just try to resize the sprite, like your's, look what i got. Strange that it's not shown in nodewebkit.
But if you don't have resized sprite's, this is probably a bug.