Have you considered addressing the issue of soft-locking with a "Narrator speaks to player" screen that explains this could cause the softlock, have the narrator specify a recommended course of action, and then have a "disable event" button that can be clicked to back out of triggering the event? You could then allow the player to enter the area without triggering that event after that screen - but the event re-triggers and gives this "back out screen" again each time you enter that area, encouraging the player to prepare for the softlock. Alternately, you could have a "disable event" or "disable progression" toggle in the MC's room or something.
Obviously such a tactic interrupts story flow. But perhaps that cost is worth paying in exchange for not having a game breaking bug or an immersion breaking game mechanic that is supposed to disappear instead not disappear?
Side Note: I know dick-all about Ren'Py code. I don't know what it is capable of successfully programming.