I used to have this very, very occasionally with my CD5X.
The way it was explained to me was that because the Naim is high quality it actually looks at all the different error notifications from the laser reading mechanism and, if it these are too high, it will not play the CD; cheaper CD players do not pay as much attention to these error reports from the reading mechanism.
... sounded perfectly logical to me but I'm not putting this out there as fact, only hearsay.
I also had an issue with the UnitiServ where it could not read a Jethro Tull album, this was something more basic though since it couldn't read other copies of this same album either. I did send it off to Naim as they suggested but I never got it back nor any response.
Whatever the reason, implies some defect in the disk and a replacement should be sought.
Allan