My personal suspicion is that sometimes quiz addresses the translations instead main game, that is usually invisible, as main game and translation have matched names. Catch is that for some time after site transition all translations was named "Translation" instead game name, so failed to be found. It's additionally could be complicated if translation is not marked as the translation, as in that case it's quite impossible to detect.
Dave fixed a lot of such errors, but I haven't tools or knowledge he have. So right now I am processing endless list of "Translation" titles, fixing it as it must be... Unfortunately, I have no endless free time for that, so I am doing it for about year, and still have about 30 pages of such titles before me (50 games per page). I hope, I'll finish this before new year... and then we'll had to puzzle about other possible reason.