We're terribly sorry for this, this bug occured because of how old Yun's route is, and Overhaul somehow broke that part of her quest.
Currently our programmer is developing a patch to address this issue. I will notify you here, when the patch will be available.
Again, sorry for ruining the playthrough for you. The only solution currently is to rollback to an older save (There might be an autosave that you can use) and ignore her route for now.