@VGR I replaced the entire field with the vanilla version and the crash persisted so it's not the script/code itself.
The only changes I actually made to the fields are adding two groups to each and the fields still crash without that (A hidden item, per group. Cloud himself is a group, Tifa is a group, etc, just so you know what I mean.)
@Sega
I skip importing the backgrounds and the error persisted.
I tested a vanilla save without hidden items or other mod stuff and the error popped up after I entered the room, left and returned. Unless it's actually possible to debug what is happening by hooking something on top of ff7, I've no idea what to do.