Yes now I understand. Sandra's part is definitely bugged, because evidently in the scene in question an image was left active (the one that remains when you leave her house), which was not disabled and therefore remains above all the others as a layer (I imagine, I don't know RPGMAKER well, but more or less all games do this even those in renpy). Changing the value of the quest, it does not change all the other parameters of the quest, such as the characters or locations to activate, it only says where you are and what you have to do, so you will definitely not find Toni... maybe
Symphony of the Night knows how to change the buggy file (map195.json)
EDIT
Good news,
Symphony of the Night has
already fixed the error (I tried on mine by changing only the wrong file) and MC exits without problems, you can download the files from
his page