The Music Room unlocked status resets if you play between ver. 0.01a and ver. 0.01b of Legacy of Lunatic Kingdom.
For example, if you have a fully unlocked Music Room in ver. 0.01a, everything will be locked again when you open ver. 0.01b, showing a bunch of question marks. If you go back to ver. 0.01a, the Music Room will also show the question marks and the previously unlocked tracks are now locked again.
Similarly, if the Music Room from ver. 0.01b is fully unlocked and then you go and open ver. 0.01a, all the previously unlocked tracks will show question marks and will remain so if you return to play ver. 0.01b. You will have to hear all tracks again in the game to unlock the Music Room.










