A few months ago 2 of my friends had their 3DS's downgraded via NNID-less DSiWare transfer from the same 3DS. One just relinked his old NNID after the process was done and the other one just made a new NNID and they were both able to play online without any problems. A few weeks later I noticed they both had the same NNID number. The Mii on my 3DS friend list changes every time one of them goes online, just like the character's name and appearance on my Pokémon Moon friend list/Festival Plaza. Since they didn't seem to get banned or anything we just forgot about it, but one of them has recently been having problems to play Pokémon Sun online with a few people (that's the only game he plays online, not sure if it'd happen the same with other games). The problem is that even though he appears on the other guy's 3DS friend list (just another guy, not the other one that also got his 3DS downgraded), he just won't show up on the other guy's friend list/Festival Plaza. The reason behind this is probably the weird NNID issue and I was wondering how can I unlink and create a new NNID for one of them without losing save data/apps/losing online functionalities since it'd suck to reset his Pokémon Sun save file just to play online with a different NNID. Thanks in advance.