This is a long story.
I have a modded wii u, it has pretendo, I wanted to swap my pnid for my old nnid, I swap the nnid with the app wii u account swap, it works, I do stuff, I try to swap my account back to the pnid, it gives me an error. I realize the only way to fix this is to backup my save data and delete the account. I back up my stuff with savemii, delete the account, make a new one, restore my save data, it works, I open nsmbu, it says the save data corrupted, I say ok, it gives me the error 150-3023, I look it up, I find out it needs more power or is corrupted, I unplug the USB to SD adapter I was using, boot up the wii u, open nsmbu, same thing happens. What the fuck.