Aerith alive.
I beat Sephiroth once.
Been using Cloud/Tifa/Cid as party leaders based on whim.
I have beaten the Caith Sith fever dream.
Gelnika cleared.
All Lv4 limits acquired.
Only missing Venus Gospel of the ultimate weapons.
Got a gold Chocobo from breeding.
~25M Gil.
Beat Ozma
I haven't beaten Emerald/Ruby weapon yet. Since I don't know the secret boss' power level I wanted to check it first.
I've likely missed a few things here and there, but generally I've been pretty thorough. Not seen an issue like this before at all.
I fixed all of the Master Materias from their caves (consequently beating the four encounters) and read about the secret boss (Calamity? Don't know who it is but the name keeps popping up). Proceeded to get smacked by Ozma then smacked it. The save crystals in the North Cavern Hatchery all say "Awoken". Got the

? item (a Save Crystal according to Black Chocobo

), but when I use it I
am teleported to the correct
place, where Barret is getting confused by what is happening at the end of the Whirlwind Maze. However, the game starts playing like normal from that point, despite being really confused about what FMVs are supposed to be playing, and I gave up around the point where Tifa is restrained and Aerith smacks Scarlet with a chair.
It's not the easiest to search for, but it seems as if there's supposed to be a scene in that place with Cloud, Sephiroth and some people I don't recognize, after which the fight is supposed to start. Whereas I seem to loop back to a much earlier point (on Disc 2, as well, despite being on Disc 3.

). So I guess some warp index is incorrect but I have no idea where or how to start debugging it, nor what I'm looking for. So any info is appreciated. I really wanna try the fight.

Oh, and this happens even if I disable all other mods except NT 2.0. So I guess the save file might have the issue itself.