I've recently tried 3 bock nibs (all new), all with three sealed cartriges, and all 3 nibs, when pointing downwards, would collect ink quickly between the fins, and if I write like that would burp the ink on paper. None of my other Bock nibs that I've had for a while did this.
Now I have another one in hand (for someone else), and it's doing the same thing, using a converter.
I am sure there is no air leak anywhere, and to be honest, 4 nibs is way too much of a coincidence. What are your thoughts please?