Any medical issue I’d say. It’s gives you a good starting point, you can just query with the vague symptoms, “my kid is floating above the bed, screaming in Latin, but has no fever”, and you’d get “it seems like your kid has pavor nocturnis, that happens with 13% of the kids, nothing to worry about they grow it out. If it happens more than once a week visit a doctor” - and now you at least what to look for. The alternative is to spend days unnecessarily with doctor visits, or ask your parents who either don’t remember shit, call a priest, or told you not to look at the kid from above because it gives them a lazy eye among other things.