Sorry, I know that this is an old thread but I have been having the same issue of clicking on NNID settings and then getting an error and then the system restarts. I have no idea what emunand and sysnand mean and I don't have any games or anything that i need to backup on my 3ds. I just want to be able to redownload pokemon bank and access it but I can't since the system won't let me login to my NNID. Is there a simple solution for me? I have reformatted the system already and that didn't do anything to help. Thank you!