Updated and tried again, but it seems to be the exact same error with no differences in the error code.
I use the itch.io desktop app, but I can say that uninstalling and reinstalling did work.
Edit: New issue(?) I managed to continue and beat Tory 3 times. She's joined, but there's no bosses beyond her. The "upcoming boss" stats stay the same and, if I hit summon boss, it just gives me the third encounter with her again.