Songs not synced properly

[tattooedmind]

I have a Droid R2D2 with a 32gb micro sdhc card. I use freefilesync to put music onto the card, while in the phone plugged into the computer. songs play fine on the computer, but some songs after i sync them and try to play them on the phone don't play properly. let me explain a little more. i have almost filled the sd card with music (<1gb of free space). the more recent songs i have added, while in the middle of playing [song1] will cut to completely different song [song2] for about 10 seconds and come back. the music app (i've tried it on 3, the stock app, mixzing, and musicXmatch) still shows [song1] is playing through the whole thing. it always happens at the same time in the song, and its the same songs as if that part of [song1] was overwritten with the 10 seconds of [song2] somehow in the syncing. it hasnt happened to any songs that have been on there for a while. its happened on multiple songs and it seems to be happening more as i'm using up the last bits of free space on the card. any thoughts on why this is happening and how to prevent it? its a little bit unnerving to be listening to between the buried and me in the middle of a nasty lick and have it switch over to dave matthews band and back again. its bad enough android doesnt support gapless playback yet.