During the first demonstration of the Face ID Craig Federighi on iPhone X presentation was a small gaffe. His reason was not the fault of the new authentication technology, but rather in its design.
Apple explained what happened:
You can reconstruct the situation with Touch ID yourself. Just click a few times on the sensor finger strangers, and after five attempts iPhone prompts for the password. The same thing happened with Face ID.
But still, there was a blooper. Yes, Face-ID technology worked as it should be, but the incident spoiled the impression from the presentation.