Hi, I'm also getting this same problem. It is only happening when I try to launch Fire emblem warriors for some reason. I am using sysnand on my banned switch and it is only coming up for that one game, every other game I have installed open without that message
although i ended up accidentally changing my nand with no way of going back bc i didn't know you needed a gamecube controller to restore it (i have a wii minus/1.1, which doesn't have gamecube controller support)
and if i find the sd card i have my NAND backed up on, i can not only restore the NAND if i solder the right part in, but i can also put my NAND on dolphin, then i can play dolphin online, like PMEX Remix or MKWii Riibalanced