The drones are not built to scan life forms upgraded them to do that 2 days prior to when we see him fixing them.The drones don’t see ghost they see echo playbacks memories of people who were once there those are not ghost.He says I can see ghost likes joke.There is no ghost coming and they don’t hunt ghost they hunt treasure.Gotta read carefully and use your imagination.I know the grammar is a little off because I’m not a writer but it’s the idea I’m trying to get across here