It is latest official rom on it? The fastest is, btw, 4.1.2. Try also, under animation scale, set it to 0.5x. Sometimes helps.
Anyway, very strange behavior for such a good phone and an official firmware. I would recommend full wipe and reset, of course, if that's not a problem, and if you saved all the necessary data from phone. And as final solution, reflash rom.
Yet, before any drastic methods,, first try experimenting with values for animation scale. If you are satisfied with the current situation, then do not touch anything.
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