That could be an area with insufficient contrast, a similar problem that early drives had when CD-Rs started appearing. In that case I would've tried a mirror or black pad (about the only thing those audiophile "disc mats" are good for...) on the top, to shift the offset level.

Note that CD uses 780nm infrared so what the human eye sees is not necessarily what the drive sees --- this is why "transparent" or "black" CDs work.