@dbm, I understand what you said, but I don't think the logic works. Say I try my thumb first and it doesn't read. If I move to my index finger, the system won't continue to compare to my thumb because of the obvious mismatch. It should move to the rest of the stored digits, finding my index as previously scanned and open. If, in fact, it is updating the thumb based on the index, then the software is totally screwed up.
@chas_m, I had heard of others complaining, so maybe I'll call Apple tomorrow to see what they have to say. I reprogrammed it the day I made the post about it (two days ago) and it's already failing 50% of the time to the point where it forces me to enter the passcode. Not much use to me.