Has anyon eever played around in a CD changer?

I took a non working Sony CDX-52 into a Sony authorised agent..  They reported that the A-250 cartridge which Sony told me to buy was incorrect (the repairer jammed it into the unit) and said it had damaged my changer and that it now couldn't be repaired.  (I now discover that I should have bought an A-10B cassette)

Does any one know how I can check the repairer's story about the cartridge having damaged the unit? I am a bit reluctant to buy ANOTHER   correct 10 disc cartridge but genuinely wonder if the repairer isn't making up a story about the unit being beyond repair because he either just got his story wrong OR couldn't be bothered to fix it? What should I look for which is supposedly damaged beyond repair inside this unit (out of which the cartridge came quite easily once I took off the cover).  I am exceptionally doubtful about his story about the unit being damaged beyond repair as I did look inside it and couldn't see anything which would be in any damaged much less damaged so badly that an authorised agent couldn't repair it.

Did you ever get the A-10B cassette ? Try to put this cassette in there and see if the changer accepts it or not.

No. obviously I haven't got any access to one or I would have tried it before putting out the message.

Is there anything inside the CDX52 which can break by the process of putting a wrong cassette into it or by the process of the mechanism trying to get the CD tray out of an A250?

Yes, the cartridge eject mechanism is a plastic hook . If the grooves in the cartridge do not match the tabs that the grooves ride on, it will either break them off or they get jammed in the track. A common occurance with Alpine changer. ( They give you a E01 error ).