My mate had this all the time with his launch console, he traded it and still gets it, just not as rare (and it happens wherever the console is).
I had a problem where Tony Hawks was reading as a "Mixed Media Disc" and wouldn't play. Nothing to do with the console, it was the disc. I hope WatchTower isn't reading... I got a wet flannel, scrubbed the disc as hard as I could and then got a t-shirt and dried it off.
The result, one disc that WORKS and it looks like it's straight from the factory, awesome!