If you quit (F6 and confirm) or do fast quit in the subscreen (B + A + Up Simultaneously) and you choose to continue, the KEY file will never respond to the quest and cheats are unavailable for the remainder of the quest usage. You are forced to re-enter the cheat code if available.
.key file doesn't respond to quest loaded in ZC to unlock cheats after Quit->Continue
Key files work on ZC?! Huh.
In any case, cheats should now stay enabled across quit->continue in general, and so this bug in particular should be fixed.
Cheats now carry over after Quit->Cont.
Bug now fixed in 536. 