Downloaded songs disappearing

[heycass88]

Hey there. Having an issue where after downloading a number of albums, I open my library and find that a number of seemingly random songs from each album have disappeared. i.e. there is no longer a green download icon next to the song titles but instead a gray one, indicating the song is pending download.

I have tried factory resetting phone and resetting the offline devices associated with the account and re downloading everything, still happening. I am saving to SD card.