Tracks disappearing offline

[blueneptune146]

I know there are a lot of posts about playlists disappearing offline, but my issue is about tracks. I just added 3 songs to my 2010s playlist on my PC and I decided to make sure these were on my iPod offline so I would be able to take these tracks in the car with me. When I did, Spotify said it was downloading over 80 tracks, from playlists that I hadn't touched. This happens all the time it seems. I turn on Spotify on my iPod and it starts downloading tracks that I know were previously downloaded and updating playlists that I've made no changes to. I'd rather have this issue over the entire playlist thing people post, but still it's a pain when you're out and about and you want to listen to that track you downloaded months ago and it's magically disappeared. Any thoughts as to why this might be?