Every time after my device reboots, Spotify changes offline storage from sd card storage to device storage. Spotify then begins downloading all of the saved music to the device storage. Changing the storage location does not stop the download to device storage, only instructs Spotify to move the files once the download is finished. Meanwhile, the storage space is still allocated on the sd card for the old library.

Sometimes, Spotify will only download a song or two before simply removing the available offline flag from most music which had previously been downloaded. In this case, often Spotify was not loaded at boot (presumably due to not having been in memory at power down) and I allowed the sd card to be decrypted by Android prior to starting Spotify. When this happens, and I switch it back to device storage, sometimes Spotify will temporarily notice its previous offline cache and allow offline listening for a time. Eventually it always resets the storage cache and insists on redownloading.

The problem seems to be that Spotify always loads and looks for its cache before the encrypted sd card can be decrypted by the system.