IDG Answers is a community of experts who are passionate about technology. Ask a question or answer one below.
It is something that other people have noticed, as the earlier post pointed out, but I’m not certain that there is much you can do about it yourself. I would try cleaning the reader with alcohol, to get all the oils that have accumulated off. No promises, but it might help.
This appears to be a common problem, according to this Apple discussion thread.
Here's a potential solution:
"Touch ID works much better with the pad or thicker part of your finger or thumb, rather than the tip. The best and fastest way to use it is to click the home button to wake the phone ( but don't hold the button down or you'll activate Siri) and keep the pad of your thumb or finger on the button to unlock it all in one move."
Here's another "quick trick" designed to improve Apple's fingerscan accuracy.