This may be of mild interest, but I do mean mild.
Awhile ago I found a way to use
Link's Awakening DX to freeze up the 3DS, by a bug that anybody can do, but of little significance.
Before, doing the glitch would make the 3DS totally unresponsive, but now the system will be aware that an error has occurred, forcing it to close the software and reboot the 3DS.
It returns to the home menu and is totally locked down, home button will do nothing, pressing power will not display the "software closed" screen. All you can do is press A or tap the icon, or otherwise press and hold the power button. Even removing the SD card will do nothing.
Does a similar screen appear when trying to use a blocked flashcart?
There are two possible reasons this is different from before, it's either the 4.0.0-7E firmware I installed today, or the update for the Virtual Console title I downloaded from the eShop today.
Whatever the reason, the 3DS knows how to handle unexpected errors differently now and I guess that kinda has some significance, it might reduce the possibility of relying on a crash to run an exploit...
It should be noted however that the "ENGAGE RIDLEY MOTHER FUCKER" password crash on Metroid (NES) will still lock up the system as before, unresponsively.