i dont know if this is a bug or what so ever...
i just noticed that when im unlocking dio...
at first im using Amy and using its mobility and double jump...
i tried it 3 to five consecutive times but i got nothing...
then i use my lire using its range advantage and... POOFF!!
every time i run the dungeon (e.g. Victor, Basilisk) i got Dio Stones consecutively...
i dont know if this will also work on you guys... but it is working for me...
notify if this also works on you....
thnx...!