when my qev leaked i was advised by nicky t to poke a small allen key into the air exhaust hole to dislodge the seal. apparently they sometimes geta bit stuck and the momentary change of air direction won't reseal them. just give it a poke, let the air rush out for a few secs then pull allen key back out. repeat a few times and hopefully it'll stop leakin. if not then its because the seals nadgered and its time for a new qev.
worth a go tho