Duplicate name error when syncing iPod Classic

When I sync my 160 GB iPod Classic on Win10 with iTunes Ver 12.13.1.3, it seems to go OK until I get a message that The iPod could not be sync due to a duplicate name (I didn't write down the exact words). When I eject, the music seems to have been updated but Cover flow has not been populated at all. That is the only problem I see but there may be others. Any idea what's going on here?