CD Changer Question

It doesnt matter what position I place the Disc in. Some discs do it and some discs dont but the majority sound scratchy.
The FM is okay so I ruled out a bad speaker.
I have tried different CD media that plays on other CD's W/O any problems and it doesnt help.
I asked my local audio guru and was told that they either play or they dont. He said the newer models sample more and that might make the difference.
Are there any tips or tricks I could use to troubleshoot further?
If I have to buy a new CD changer are they all compatible with the Bose system?
Thanks for the help,
Mike


