I select the SD card in the Spotify storage settings and then download some songs. They correctly show as downloaded and the 'Currently using' entry increases to indicate they have been stored on the SD card.

However, when I restart the phone and then open Spotify no songs appear as downloaded. When I look in the Spotify storage settings neither SD card or Device Storage is ticked. If I then select SD card I get the message telling me that Spotify is changing the storage to the SD card but on completion none of the downloaded songs are there.

I can then successfully download songs again but as soon as I restart the phone the same problem happens again.

This is making Spotify unusable for me as I frequently need to use it offline so unless this can be resolved I will have to cancel my premium subscription. 

Spotify version 8.4.38.621

Sony Z3 Compact

I've tried a clean install but it still has the same problem.