Item description:

If you save a game and then Quicksave it, you’ll return to the title screen where you can then resume your Quicksaved game using the Continue option if you choose. However, if you instead start a new game, you will be warned that doing so will cause the Quicksave data to be erased. If you do this, then meet certain playable characters in the new game, then get annihilated without ever saving, the game will reload the previously saved game, but those characters that you met will suddenly have low Levels, high HP and 999 MP. This opens the door for lots of grinding to supercharge all of the Returners’ stats.

If this patch is applied, the game will instead return you to the title screen, as it should. This bug is exclusive to the US and European releases of FF6 Advance; the Japanese release does not have this bug, nor do the smartphone versions of the game.