Offline tracks, gone (again)

[WinterEagle]

All my downloaded tracks on the android app are gone, after I've seen some songs become unavailable offline, then got to relogin because the app crashed. All playlists and artists set to "offline" become not offline, without my permission. The storage option suddenly changed from the SD card to internal storage, but the space in the SD is still occupied. It's like an auto-delete cache. I'm on a Samsung galaxy j6, and that used to happen on my zenfone 2 as well. Tried rebooting, but they are still gone. What can I do?