Yes seems like a bug with the newer update.

As I suggested, what you can do is instead of using iTunes to open the audio files, choose VLC - (click on link). To use it to open audio files, you can right-click an audio file & choose Open with ..., click Choose Program ... , then choose VLC, and check the option with Always use the selected program to open this kind of file.

VLC can play more audio formats than iTunes can & is highly reliable for finding if a file is bad/corrupt/fake. And by using VLC, will mean no partial preview files end up being imported into iTunes.