someone buys a horn, hears something and contacts us (with their very first post) not the seller (or their teacher,.....).
Most of the time, players do not hear airy things that come out of the bell. The only source for that audible of a noise would be the spit key. That, on the other hand makes no sense because F, G# and G (especially with 1+3) all supposedly make this noise. Those notes have the pressure nodes spaced far apart. That would probably rule out the leaky waterkey.
My suggestion is to have a player better than you try the horn. I suspect something in your practice room is more resonant than the horn.........