Every time my phone is rebooted for some reason, Spotify reverts the storage setting from SD to internal. It seems Spotify is starting before the SD card is fully mounted and there are multiple support threads, going back many years, about this and it's still not fixed. They've ignored years is requests to sort this and as such, it's still not possible to trust the download feature of the app. It's a real shame because the service is great otherwise. Support doesn't seem to care at all.