Alright so after playing Rhythm Heaven Fever for a while I exited to the wii menu and everything was fine until I clicked to go back to the Wii U menu. Instead of rebooting back to the Wii U however, I got a black screen with white text saying "The system files are corrupted. Check the Wii operations manual for help and support troubleshooting" and so I turned off the Wii U and then turned it on again and went back to Wii Mode. Everything was fine and there was no sign of "corruption"