My Brera didn't come with a manual for the 10 stack CD changer only the Blue and Me hands free kit, so I'm not sure if this will help anyone.
When I loaded the CD changer it indicated on the dash that it was scanning 10 Cd's but would only register one disc and would not recognise any of the other nine discs. After reloading and reinserting the changer several times, I was able to get it to recognise two discs and change between them. Since then by allowing the CD player to play the last track of each disc, it will load the next consecutive disc. By allowing it to do that with each disc I was able to get the car to recognise all 10 and be able to switch discs without any issue.
This is probably the process in the manual, but as I couldn't get access to a CD player manual for the 159/Brera easily online or find any instructions in the forums I hope this helps anyone with the same problem.