The read error with a scratch-free CD-R is very common. It's due to heat.
A stamped CD is made using technology (and with materials) which are not very susceptible to heat. But CD-R, DVD-R, etc, need to be "burned" with a laser when being recorded, therefore they are made of different material, which can be modified with heat. If you keep a CD-R on the dashboard of a locked car during a hot day, the CD-R is almost guaranteed to give data errors. A stamped CD will not show any problems.