idk I mean if you really get down to semantics, the descriptions themselves change throughout the books. The most glaring one I can think of is that in #4 Ax only had one nostril. But little things, besides that--I think in #7, Rachel says you wouldn't be tempted to ride Ax because his back slopes too much, but Loren rides Elfangor just fine in the Andalite Chronicles, and the size seems to change a lot. Idk, could just be me, but based on the fact that Ax is, at the very least, an old adolescent, Gafinilan ain't no Clydesdale horse if Ax is just a deer.
Taxxons change a lot too, but Hork-Bajir don't change so much, only because I think their descriptions are appropriately vague...we know they have wrist, knee, and elbow blades, but exactly where do these blades actually emerge, and what direction do they point?
I think about this way too much, sry.