That bug is in the original globe too, I never found the cause.
Oh!! Okay then.
Watching how this bug appears, I may conclude it somehow connected with coord caching things (if any). I can try to figure out how to fix this.
And I prefer the noiseless look too but I've never liked noise/dither smoothing anyways.
Dither is nothing like noise in this case. It should be looking much better. But due to the nature of this "shader" technique I can hardly imagine how to integrate dithering algorithms into this shader.
Dithering requires access to whole "undithered" image with 256 intensity levels of shade.
Actually I see only one way - using 8-bit shade mask on "unshaded" globe image, like post-processing.