Funny thing about demons is they always seem to obey the rules and logic of the beliefs of the people that "experience" them. That alone should be a tip off that demons are a result of psychology, sociology and culture rather than an emperical fact of reality. Demons disappear or relenquish control if you say "jehovah"....if you believe they will, they will cower and hide from a cross as long as you think the cross is holy and has power over demons, they will refuse to enter your house if you sprinkle lambs blood on your stoop if that's what you think keeps them out.
Even the objects or circumstances that summon demons vary depending on religious belief, but every one of them is correct, because for those people it did "summon demons". A copy of the New World Translation summons demons for fire and brimstone baptists, and a tract on hellfire and brimstone will summon demons for a JW. A JW would claim that a cross summons demons, while the baptist successfully expels demons using a cross. And it's amazing that exorcists of every religious denomination seem to have success in expelling demons....of the people that believe they can expel demons.
If the only consistent thing about undocumented "mysterious" occurences is that it seems to always line up with the prejudices of those experiencing them, then it's a safe bet that it's not a matter of reality, but one of psychology and culture.