Sound person in the jam, jumping in since you flagged music/sfx as not there yet. For a station imposter game the money sound is the tell that's half a beat wrong: a footstep, or a door that closes a touch too soft. Keep one low ambient bed under everything (fluorescent buzz plus distant rail) so the quiet parts read as listening, not empty. The train-attendant premise is a good hook. Happy to trade ears if you ever want a second listen.