Many songs not playing offline

[alisonheller]

I have several offline playlists on my premium account (nowhere near the 3333 song max). However, even after syncing, many songs will not play offline. I'll be out for a run and my playlist will just stop when it hits a song that won't play off line. What makes it worse is that some songs will play a few times and then never again. Every time I play music offline, more and more songs are "dead." 

Why is this happening? All the songs and playlists play just fine on desktop. Just offline mode on my iPhone 5S.