Karaoke selection number not play on copy of SD card

[nowIknowthewords]

Hi

I have a Starsinger S1000 Pro11 HDMI Karaoke machine: http://www.emkaraoke.co.uk/contents/en- ... _Play.html

I have got all the CDG & mp3 files plus a 'Card Song List.txt' files for all my Karaoke tracks on an Class 10 SD card.
It works without problems when a Karaoke track number is selected.

When I copy this SD card for a backup, it does not work.
When I select the appropriate Karaoke track number, the wrong track is played.

I have tried 3 different SD cards, all with a Class rating of 10.
I have formatted each card prior to copying the master card to it.

Any ideas why the Karaoke track references for the karaoke songs gets changed when I copy the 'master' sd card to another sd card?

Many thanks for any help.