thats odd usually all you have to do to get them to leak again is just put gas in them when they leak.... maybe their being used at a funny angle
like the bike is on a rear wheel stand and it's ass is real high in the air...
or maybe it is the front wheel being held too high.
....
that's a real pickle buddy can't have leaking carbs but if you can't get them to leak again just double check the float level and send them back !
.....
Bob.......