shift2win

I've searched and read all the threads concerning the lexus cd changers, but never really got an answer to my problem. I've got a 00' GS4 with a Nakamichi headunit. When I got the car, it didn't have a cd cartridge in it, so I bought one off of ebay. Put some cd's in, and it would only play disk 6. Then one day it started to randomly choose which cds were loaded when I put them in, so sometimes it would only play disk 6, and if I ejected the cartridge and put it back in, it would read and play disks 1, 3, and 6, etc. I could live with that, at least it was playing some, but then all of a sudden I got an err 5 code. After playing with it for a while, the err 5 changed to an err 2. Now it doesn't read anything, when I put the cartridge in, it goes from slot to slot, when its done throws an err 2 code. Any ideas or am I gonna have to replace the cd changer?