Have a 2000 s430 in the family, and the NAVI system does not recognize the loaded NAVI CD. Error msg reads disk not loaded.

About two years ago ejected the original CD, then I loaded the updated CD and the CD drive made an awful racket at first - probably a near- death rattle. Now, feeding the second older disc into the drive causes the NAVI system to eject both discs. Otherwise, nothing but the disk not loaded message.

Is this a common weak point and how best to resolve.
Thanks for hints.