Ive done a bit of digging, and it's completely random. I don't even use Rosalina injection and I've been fine the whole time, though this may be because I recovered from an original S/M ban with a personal seed and a changed console ID. Anyway, there's truth to the fact of turning off spotpass... To an extent. No matter what you turn off, whether it be spotpass or sharing info, Nintendo always has access to the title Id of the app you're playing. This is what is confirmed as fact so far. What is speculation is that the bans are caused from people running invalid title ID's for frograms such as freeshop, though this is still most likely the case. You can't assume the people being banned are all lying or doing something stupid. The cause is unknown and seemingly random, and the most we can do is turn off everything and use Rosalina injection, which so far has been keeping people safe.