I'm going to try to speak about something I don't fully understand, but isn't basically his fault for not having practiced a script with the interpreter??? I bet the stuff that was lost in translation was pretty technical or strongly game related, including lots of obscure game company names being thrown around.
My guess is that he didn't plan anything and the interpreter(s) rightfully complained. Of course this is only my shitty opinion on the matter.
If he was working on a shoestring budget I'd give a pass on it, but the Kickstarter campaign raised about $115,000 USD. He should have been able to find top notch talent over there with that kind of scratch.
It's kind of an apples to oranges comparison, but David Munoz was able to use a little over $7,000 (for the Service Games: Rise and Fall of Sega book) to take Sam Pettus' original version, hire a professional editor, finish the editing process, acquire and clear images and copyrights, send out pre-release soft cover versions to backers as a preview, and then produce color and black & white options for e-book, soft cover and hard cover versions of the book, including commissioning a cover art piece. He's done a damn stellar job with everyone on a shoe string budget.
$115,000 should have been enough to get him a month in Japan with room and board and expenses (being budget conscious of course, as I hope he was), equipment, professional translators and interpreters with enough left over to take 6-months to a year off of work to finish up the editing and compiling of the book.
There's always more than you budget for I have to imagine with things like this but $115k is a lot of cash to work with.