I am making a map and celeste crashes when I enter one particular room. (The game stays open but it shows the "oooops" screen that says "Celeste/Everest encountered a critical error"). I did some testing and it seems like the crash occurs when the player enters a room from below, and the room they are leaving contains a Theo crystal.
I am also using a code mod that I wrote that has to do with Theo crystals, but the crash still occurs when I have it disabled, so I don't think that's the cause of the issue.