After the iTunes update to version 12.4.2.4 on 7/19/16, I can no longer remove audiobooks from my iPod nano 7th gen. I can drag and drop new titles from my iTunes library to my iPod, but I can't get anything off my iPod. I'm running OS X El Capitan v. 10.11.6 on my iMac. Does anyone have some helpful advice?

Thanks,