My Japanese Wii U, which is in pristine physical condition, plays EVERY SINGLE Wii game without any problems, no matter what the disc looks likes. However, when it comes to playing Wii U games, there have been discs I've bought that the console simply can't read, even though those discs appear to be in perfect condition.

My guess would be that there are separate lasers inside the console, one each for Wii and Wii U games, and the latter requires some form of maintenance/cleaning. Is that possible? Or if there's only one laser for both types of games, perhaps Wii games are more easily read even if the laser requires cleaning? I'm not an expert (obviously) about the technical side of the Wii U.