One D&D issue that @reverse brought to my attention—it was nine years ago that we had this convo—is when a module's room description has something happening just as a party is about to enter a room.
Arden Vul has a mix of room types:
• there's a tiered roll-table system for who is there and what they're doing / what they want
• there is a schedule of hours (sometimes combined with probabilities)
• there is just a probability
• and a few that are just "the prisoner is dying and will die within three rounds of the party entering".
I think this is a fine mix but that last type can undermine the other types. It's instantly noticable by the players as feeling "fake", and it can make other things feel similarly fake. They've been sneaking around in a prison lately and at one location there was people being there just twice per day, and the party happened to leave there the exact same time as those NPCs were arriving (at our ten-minute-turn granularity). That sort of awesome timing accidents really happening for real is to me a lot more memorable and awesome than any "scripted" room has ever been.
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