When I first installed the app, it contained all music and sound effects from a game I've never played, and none of mine. Deleting the cache didn't fix it.
I reinstalled it, and it seemed to work fine, except for some song titles (I could listen to it, but it said 'Unknown title'), artists and albums missing. Also, deleted songs stay for all eternity: I changed the tags and titles of some songs and deleted the old ones, but now they are duplicates (the old ones give me an error though). Deleting the cache had no effect.
Today, I found another song called "bit remix", which was a chiptune cover of a popular anime's ending theme. It was nice, but I had never heard it before. Reloading the titles and deleting the cache did not fix it.
Why is it so buggy, and why do I see others' music collections?