Where have you made this mess? You can't set that info directly on the Kindle, so have you been using some sort of ebook manager?
And how many messes are we talking about? Dozen or hundreds?
If you are using Calibre, you could certainly use a regular expression to fix all the metadata. You might end up having to reconvert the whole library to get it reflected on the Kindle. Not sure. Even if so, it could take a while, but it would an automatic click-and-leave process.
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