That could be the problem - You might want to clean the lense if it can be located easily. Other than that, you need servicing, or might be better to get a different one. There are better sounding ones like onkyo mini on ebay for a little over $200.
I have a MHC-C70 too, and have same problem. Unit is over 10 years old. I took it apart to see if I could easily get at the lense, but it really looks like it is in the middle of the tray/changer mechanism. Guessing that buying a new system is going to be cheaper than service.