I own a 8310 an my keyboard is rock solid. My 8310 is 4 months old and no dust under screen and no keyboard rattle.
P.S. I think you should get it replaced while you still have the time to do so.
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BlackBerry 9650 6.0.0.280
Platform 4.4.0.185
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8100|8300|8310|8320|8900|9000|9700|9650
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