Starting recently and with greater regularly (now daily) I find that all the downloaded albums have deleted from my android phone. Strangely playlists are not affected, but every day this week I find all my albums have gone. I download them again over wifi in the evening, they are there for a while but within less than 24 hours they have gone again.
I have followed advice around clearing the cache. Also found and removed offline devices that were not correct. Neither have worked. As I listen daily on my commute, I'm now getting pretty fed up and considering moving service.