iPod Classic keeps freezing, won't play certain songs

Last week I added some new songs to my iPod. I hadn't synced it to iTunes in ages until then, and that was the first time since I'd updated iTunes to version 12.1.2. The software on the iPod is also the current version. Since then it won't play certain songs. A song will be fine one day but won't play the next. It shows the playing icon next to songs but the timer is frozen at 0:00, and it'll skip ahead before they could actually finish playing. It'll also take it's time loading between screens sometimes, usually before a song that won't play.

I didn't drop it and never had a problem with it until now, the problem started immediately after I connected it last time. I've tried resetting it and I've tried connecting it to iTunes and restoring it. I just connected it again and I'm getting a "could not be synced, and unknown error occurred (13010)" message.

Any ideas?