I use my 64gb card for all my music. Most of the time it'll playback everything fine, but once in a while it seems like it'll make a multiple duplicates of every mp3s I have stored on the card (not the ones that are on the phones internal memory). Sometimes when I'm even playing the mp3s, it'll stop midway and say the file isn't recognizable. All of this isn't fixed until I clear out the data from the memory storage where all the unplayable duplicated files are deleted.
It's a Galaxy S2, Android version 4.0.3
It's a Galaxy S2, Android version 4.0.3