I've seen something similar (a long time ago) where the scales were sort of "de-laminating"...but I'm sorry to say I do not know what causes it. Sorry that
your vet apparently doesn't either. I'm hoping someone who knows more about this will chime in? If not, we can continue to brain-storm this here... (And
I don't know what ever happened with the one I saw before...it was many years ago. It also had some of the notched scales like yours too.)