As it seems like this is a bug, I would appreciate it if as many people as possible could send feedback about this issue to Apple. I just did and filed it under macOS.
https://www.apple.com/feedback/macos.html
Here's what I wrote:
After upgrading from 13.1 to 13.2, I can no longer sync my iPod Classics with my music library in the Finder. But reverting back to 13.1 fixes the issue. And other people are having the same issue as well.
After connecting the iPod, it goes into 'Don't disconnect' mode, as it should, but after a few seconds, it disconnects and shows the main menu again. But in the Finder, it looks like the iPod is still connected, so when I try to sync, as the iPod is actually not connected, the sync fails.
The error messages I get are "The iPod cannot be synced. An unknown error occurred (-25170)" or "The settings were not saved for the iPod because it could not be found".
I would really appreciate it if this could be fixed since many people are still using their old beloved iPods.