Problem copying my iTunes library into crates

I’ve followed all the instructions and copied my iTunes playlists into crates and than transferred the crates into my internal HD, the problem is that circa 200 songs are missed. I’ve repeated the operation couple of times but the result is still the same. Please help

Hi, aac protected files won’t be copied. There also is a random bug with some mp3 files. Try to copy them by draging them into new crates/playlists manually created.

I’ll try but first I need to understand what tracks they are…