I have a (roughly) twenty month old normal ball python named Rogue. I've had him for about fourteen months and in that time he's never been a picky eater and he isn't nasty in his personality. Oh and he's never been sexed so the "he" is just an assumtion.
When he sheds he always fails to shed all the scales on his head. I haven't noticed any retained eye-caps but he has scales on his head that don't shed. His body sheds just fine but his head doesn't. He has a moist hide to help with his sheding and I try and keep a higher humidity in his tank than the house.
Here are a few pix of the retained scales.
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