Regarding progress on the NG+ bug, I speed-ran the game + expansion in the Japanese version, got to the true final boss. Saved, finished the boss, entered the basement, saved to another slot. The second save loads and then starts NG+ properly in both language versions of the game. However when I reload the first save, do the true final boss in the English version, and then move on to the basement, it will not let me restart.
Between this, and the fact that by removing the the code that makes the game remember what your stats/inventory/etc were before entering the basement, seems to suggest that, as near as I can tell, something is not carrying into the basement properly, so when the game tries to exit the basement, it tries to find that something and gets screwed up. Or so it seems.
Still no promises on being able to fix it, but for the next phase, I'm going to see what, if anything, might have gotten changed in the code between the two versions. If/when I have more news, I'll report back more.
Between this, and the fact that by removing the the code that makes the game remember what your stats/inventory/etc were before entering the basement, seems to suggest that, as near as I can tell, something is not carrying into the basement properly, so when the game tries to exit the basement, it tries to find that something and gets screwed up. Or so it seems.
Still no promises on being able to fix it, but for the next phase, I'm going to see what, if anything, might have gotten changed in the code between the two versions. If/when I have more news, I'll report back more.