I once read something about the Noodler's Ahab being fairly prone to random slight leakages due to indeterminable reasons, which is in line with my own experience. Not moving the pen too much solves the problem - usually, although I definitely had the occasional leakage despite that - but that makes it a fairly bad daily writer, obviously.
My best guess - although it's really just a guess - is that there's a problem with some of the feeds. It almost seems as if the surface tension of the ink is too low to stay in the feed, so it ends up dripping out at the slightest provocation.
It does not seem to be the fault of the ink as such - I used to have Pelikan 4001 bl-bk in there, because it's a dry, very well-behaved ink, with the result that it both still leaked, and ran dry after half a page of writing.
I feel your pain, though - I inked my own Ahab again today, and I'm so sad that I'm hardly able to use it outside of my own home, because I constantly have to be afraid of ink leaking everywhere. It's a shame, because I really like the feel of the pen as well.