Interactions with physical objects
Nicole Kidman's character is always carrying oil lamps around, and the shotgun. As well, as closing/opening doors & curtains. She closes and locks the piano fingerboard and keys.
"The others" (the new family and the medium) apparently witness her opening and closing doors and the curtains (though not her apparition). Also yanking covers off of furniture in that one room. As well as closing up the piano. Which, presumably the father, then re-opens. Who also has an apparent door "battle" with Grace.
So did the new family/medium witness oil lamps and a shotgun floating around and moving in and out of rooms? What about the children's books and toys?
Or is the just the kind of plot hole viewers aren't supposed to wonder about in these movies?