[Ask] MyDefrag for Flash Disk Defragment + FM Modulator

I have a flash disk which I only use for FM Modulator in my car.
FM Modulator = i-Mobile
Flash Disk = Sandisk 2GB
All the files in my flash disk are in MP3, so I can listen to mp3 in my car.
My FM Modulator read the files in accordance to the order I transfer the file to the flash disk.
So if I put B.mp3 first, then A.mp3; FM Modulator will play B.mp3 before A.mp3.
So, to change to song order, I usually move all the mp3 files back to my hard disk (empty the flash disk)
And transfer the song one by one according to the order I want it to play.

Recently, I've tried to defrag my flash disk using the new feature from MyDefrag.
But after that, when I tried to use the flash disk with FM Modulator again, a weird thing happen.
After playing song track #1 in FM Modulator, it jumped immediately to #267 for example.
And if I try using the remote to previous or next, it will choose the next and previous randomly.
It behaves similar to being shuffled.

I tried reformatting my flash disk and adding the song one by one to fix this, but it doesn't work. It keeps reading the song randomly. Please, I want to make my flash disk back to normal. How to do it?

Thanks.

I am actually reposting this from the MyDefrag forum because I have no answer there, I hope this is allowed.