Well, perhaps it's just a bit sluggish as the phone portal's processes are being shutdown by the operating system, and sync gets done on the phone's system. After reading you comment, I've checked this out, and there seems to be slight stutter during the unlocking animation when I've just synced. Doing the unlock motion and pattern too fast will lead to failure, and if you're anything like me, when you unplug the phone is usually when you are most likely to be "on the move" or in a bit of a hurry to access the phone to check on the changes. This does lead to a higher rate of unlock failures.
So far as I can judge, all my unlocking motion failures have been of my own fault. I'm sometimes simply too fast. This is a phone, accomplishing a software task, and as such, it does have a certain latency which, if exceeded, may result in a lack of response. Human reflex movements can be incredibly fast. So fast, in fact, that even one's own brain might not even properly assess what he has accomplished, and if there where "errors" in an intended motion.
Just as an experiment, and because it has a nice "geek factor", try using a webcam to film the action. If the deformation of the finger tip changes, perhaps the perceived contact of your finger with the screen is not quite as good as you think throughout the whole motion... If the fingers does keep a steady contact, then perhaps your right. Whatever the case, having a Youtube of the Atrix would be interesting.
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