animated gif quality on larger export

Exported in Quicktime Animation codec: uncompressed, millions of colors. original is a png file full, smooth color. the output size matches the original image sizes perfectly (1028 x 1417). any ideas? thanks!
I just tried it again at a more conventional size 1024 x 768 4:3 ratio, and similar results (forehead region most notable). you can even see a couple of dropped pixels in the cheek area.
I just tried it again at a more conventional size 1024 x 768 4:3 ratio, and similar results (forehead region most notable). you can even see a couple of dropped pixels in the cheek area.