http://www.macnn.com/articles/12/11/09/may.be.caused.by.touch.panels/
iPhone 5, fifth-gen iPod touch show diagonal swiping issues
updated 01:52 pm EST, Fri November 9, 2012
May be caused by touch panels
The iPhone 5 and the fifth-generation iPod touch are both showing problems with handling diagonal swipes, accounts say. While the devices should work properly with regular gestures, quick diagonals can cause response to drop off. The issue is reproducible in multiple apps, and in iOS 6, 6.0.1, and the 6.1 beta. Other devices -- like the iPhone 4S and the fourth-generation iPad -- are said to be immune.
The nature of the glitch may suggest a hardware problem, since the iPhone 5 and fifth-gen Touch each use the same 4-inch touchscreen. Most users are unlikely to be bothered by it, but it could cause trouble in games, which are more dependent on rapid gestures in multiple directions.
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Joined: 08-27-08
I suspect this is a firmware issue related to the processing of the in-cell touch technology, which is new on the iPhone 5. If it was a hardware issue, it's unlikely if would stop responding after continuous swipes. It appears there is a software buffer used to queue the touch events that is not being cleared quickly enough to keep up with continuous swiping. Once the buffer becomes full, subsequent gestures are lost until the processor clears the buffer. Once the processor clears the queue, the swipe action can start again. The question is why diagonal swipes take longer to clear from the event buffer than vertical ones.