galaxy 3s notification on vibrate mode..

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http://androidforums.com – So.. when i put my phone on a vibrate mode (not silent). Some apps dont vibrate when its supposed to.. like when I get a facebook msg or a kakaotalk msg(sms app) etc etc. notification works fine when i put one the sound but nothing in vibrate mode. I checked all the setting for each individual apps and they all have vibrate and notification checked.. anyone have any idea why this is? Thanks! (General)