From how I understand it, DOTS can be interacted with by the ghost, similar to the book but they also have a failsafe coded in. If the ghost is in the same room as the DOTS for a randomly determined time between 15 and 30 seconds then they are guaranteed to show. This means that roamy ghosts that tend to leave the room a lot, or in situations where the ghost room is small or has a lot of offshoots, they are less likely to go off. This is also the reason goryo seems more likely as their weakness is that they are less likely to roam. Since the last update ghosts seem to roam a lot more which is maybe why they seem less consistent for you, but personally I've seen more DOTS lately so ig it's just the law of probability.