Seems to solve the problem... for me and a few other people who posted here on this thread.
I mean because formatting resets a lot of things like friend code and whatnot.
There's alot of years i've poured into those streetpasses, i guess its a personal thing. Plus losing all my friends codes would be a bummer.
Probably just gonna have to settle not being able to downgrade (this time around...)
I mean, i'm not even into piracy. Really only wanted to do NAND backups and dump all my cartridges onto my sd card for covenience. RNG gods or whatever, whyyyyy T.T