Scratchy Sound on Audibook

I downloaded an Audiobook from iTunes. Sync'ed it with my 2 iPod Classics. Both versions are 'scratchy' and non-listenable. It's OK on each version of iTunes that I run on Windows 10. Other books downloaded at the same time are OK on all platforms, including the iPod's. I read a previous support post with people that had the same issue with other Audibooks and followed the recommended steps (even though there was no resolution on that post): Delete from iPod and re-sync. That didn't work. Delete from iPod and iTunes, download again from App Store and re-sync to iPod. That also didn't work. Help.