@Graham Hurst:
You might want to install the add-on/plug-in QuarantineAndScrub. Misplaced and Malformed metadata is exactly what it is designed to fix. It saves an enormous amount of time. Among many other tools, it comes with over 16K Authors already in its database to aid it in parsing out the wheat from the chaff.
https://www.mobileread.com/forums/sho...d.php?t=247425
Also download the .jar file that is really a .zip file, and follow the detailed instructions in the User Instructions.
DaltonST