I already used the search but found no answer to my question.
Here it is:
I'm playing the career/storymode right now and I completed the cavern, doing every song with 5* - and I should've unlocked every photo for that part, but I didn't. There's one missing, the game says "To unlock this photograph, you need to collect 20 stars in the cavern 63-challenge."
What to do? Note: I didn't finish every song on expert, I saw her standing there is just way too complicated.
Would be glad if someone knew what's going on!