I think this was a bug that was around a while ago. When playing a 2.10 quest, if you emerge from a passageway or item room on screen 80 into a dark room, the candle won't light the room anymore until you leave the room.
Candle doesn't work in dark room after passageway - build 357
Yeah, the lighting is completely screwed up: coming out of caves into dark rooms sometimes doesn't make the screen dark, and you can walk into item rooms, use the candle, and make the room "superbright," screwing up the palette.
Ugh, the lighting code is ultra-convoluted. 😞
I'll have to come back to this fresh tomorrow.
Lighting code has been revamped in the next build. Please test aggressively.
This particular bug about being able to light up rooms after being in a passageway/item room has been fixed.