Autofahrer 🤝 Fahrradfahrer (so soll es sein)

Absolutely ahistorical comment. The GDR denazified much more thoroughly, especially in the conservative /monarchical-leaning juridical branch, with well known consequences (eg, lack of judges with proper education). You can make a point that the ideologically loaded suppression was fostering an resurgence after the fall of the wall, but what you write is .. false.

Meinst du Aktionismus? Inwiefern ist das reaktionär?

Thanks for the helpful comments, I will try your suggestions out (I am traveling atm so my inks are not readily available)! A stupid little thing I've just tried is to fill the cap with water ... and it leaks quite a bit, where the fancy "edge" is situated. So that might be the issue

Ich mache mir auch keine Hoffnung davon wegzukommen. Aber zumindest einen alternativen Zugang für die zu bieten, die es nicht haben wollen, das wäre ein Fortschritt.

Do you mean you screw the converter a little to lower the piston and that gets it going again?

Yes, that's what I am doing. I had no trouble with the cartridge I used before, so I could try that again to identify the converter as the issue. The ink is Parker Quink Black (but two decades old, so possibly alcohol-based? I read something about a change in formula). It is supposed to be one of the more reliable ones.

If I don't have problem with a cartridge, then I can exclude the cap as the source of the problem, right?