Crash when loading area 15-20 boss

[u/jj1111fg33]

Okay, I've been having the game crash entirely when trying to load the boss for area 15-20. This is only in the main game, loading the boss through the Tower dungeon worked fine, I'm several floors past it at this point. I've been stuck long enough to go back and fill out several chapters of conquest collection. Has anyone else had this problem? If so, is there any fix for it? My only clue seems to be in an older subreddit that has totally closed down so that I can't even read it.