Some of my songs downloaded songs won't play offline

[Taray]

I have Spotify premium. All of my songs are downloaded as are all of my playlists. I was listening to my musical playlist on shuffle offline and everything was going good but then for some reason seasons of love from rent wouldn't play. I took it off offline mode and it started playing. But I put back to offline and it stopped. This happened with a bunch of different songs. This has been happening for a couple months and when it happens I have to uninstall and re-install the app and it works fine. But I shouldn't have to re-download the app every few weeks. Especially since it takes over an hour for all my songs to download. I want a permanent solution for the problem. Help me please.