Been using the iPhone X since launch regularly (and who hasn't) and noticed a security feature that locks Face ID if it thinks you're trying to fool it. Has anyone notice it? If someone else tries to unlock your phone via FaceID it will most certainly fail, but if the phone is passed to the registered owner and tries it again immediately after (without turning the phone off), it won't unlock until you actually turn the screen off and on again (or hit cancel and swipe again). I discovered this when I was showing off FaceID to my friends, and every single time it did this, which was kind of embarrassing. Similarly, if FaceID fails to recognize the registered owner's face the first time, it will not function until the phone is turned off and on again or cancelled and swiped again. As far as I know, this is not in Apple's documentation online so if anyone thinks it's failing on them, think about my observation above.