This is just a theory. Maybe Nintendo has placed a finite counter on the SysNAND of N3DS's before it completely turns off and stops functioning. As there have been cases where people have bricked their SysNAND's (myself included) due to restoring the SysNAND a lot of times. There is another case I know of where the guy has his SysNAND bricked, but his EmuNAND still functions with A9LH. Thoughts guys?