I have 4 fingerprints memorized on my Xperia X without issues, and even if I do sometimes have to try a couple of times before the fingerprint reading actually unlocks the phone ("adjust your grip", "fingerprint not recognized" etc.) I have now learned how to use it so that it unlocks the vast majority of times at the first try. I even have a pretty thick hard plastic case from Caseable on my phone. I guess I'm just lucky