Thank you for your anwer, the firmware fails to flash successfully, the LED continues blinking red and green. I don't have an arduino, i have a Raspberry Pi 3b though.
I have backups of it, and backups of those. But i can't use them since the RCMLoader is no longer seen as a drive to place my backup unto, not recognized in any partition manager either.
@Xdqwerty, Osu! Tatakae! Ouendan! is the Japanese version of the game, different settings/characters/songs but otherwise identical mechanics. I played that before I knew about Elite Beat Agents lol. Both fantastic games https://en.wikipedia.org/wiki/Osu!_Tatakae!_Ouendan