So recently, I began a Fatal difficulty run on the Xbox version and stumbled on some bizarre behavior.
I'll describe it step-by-step, just in case any details might make it replicable.
On Night 2, I went to the Hidden Passage using the Angry Mask as usual, fought Blinded again and grabbed the Happy Mask from the Mask Room. Went to the Buddha Room via the Square Garden and got the Reflection Mask after beating Munakata. When I got back to the Mask Room, I realized that I had forgotten to take the Angry and Joyful Masks from the Hidden Pass, so after hanging the Sad and Happy Masks, I went back, grabbed the other two, and hung them in the Mask Room. After getting the Blinding Mask and returning to the Hidden Pass, I saw that the Angry Mask was hung on the doorway to the Entrance. I had to double-check that it wasn't the Reflection Mask. It wasn't. I went back to the Mask Room and saw that the Angry Mask had been moved. In an effort to prevent any further state glitches, I returned the Angry Mask to its rightful place in the Mask Room, then proceeded with the game.
From here, everything seemed normal. But then tonight...
During the Final Night, I noticed that all save points were deactivated (colored "red" and not "blue"), and the entrance to the well was also locked (sealed by some ghost's power, according to the message). Because I can't enter the well, the game is effectively impossible to finish. Replaying from a save point from late in Night 3 does not change the state of this.
I have no idea if these two mishaps are related, or if I could have even prevented it somehow through different actions during Night 2. I do have a save from right before the initial glitch, but I'm hesitant to retry from that point if the Final Night is doomed to end in the same way.
I might need to restart this run, unfortunately.
What a shame; I was so close to the end. At least FF1 isn't all that long.
I tried restarting from Night 2, right before entering the Demon Mouth for the first time. It wasn't long before I encountered another anomaly: after I finished the "Kagome Kagome" puzzle, the wall scroll disappeared from the Doll Room. I think it's safe to say that the state of the game was wrecked before the Mask Room incident. (Nevermind; the scroll was on the other side of the wall. Egg on my face, I guess) I'm just restarting this run completely. Let's hope that the next one stays clean.
Just replayed from the beginning up to the Final Night again. I encountered no noticeable glitches this time... until the Final Night, where the well was still locked and the save points inactive. Either bad luck, or broken game file. Unbelievable.
Well, I just couldn't let it go. I kept playing around with my game anyways, and realized that the Final Night issue wasn't a glitch. Fatal mode requires beating the extra, Xbox-exclusive armored ghost in order to proceed, and forbids additional game saves. I never noticed this in my initial search. I guess I'm gonna be the butt of jokes for awhile!