Stock CD player keeps dying

I have an 04 Envoy that has the radio controls on the steering wheel. When I push the source button on the steering wheel to change the radio over to the CD player, the cd player frys. The radio continues to work but the CD player will not play or turn on. Even when pressing the source button, it skips right over the CD player.

Now, I have had this unit replace 3 times by GMC and this is now the 4th time. What can be the problem? I am getting sick of having to take it to get it replace and then have it break again. Any comments are greatly apprecieated!! Thanks in advance