Well I checked it again and it was more a tricle, then fast drips. So I opened it fully for a few seconds, and tapped it a few times when it closed, and for now it's dripping pretty slow, hopefully it will stop.
IDK how old it is, but I do remember watching something that tis is how they fail, they get barely used, and then get used, then just break somehow.
If I was do sit down for a whole day, just with calculus and some physics, and the EE analogies, I'd probably derive most the basics of fluid dynamics. I remember that dV/dt=A.v. Which won't apply much for my pipes though, since they are all about the same size everywhere, there's no standind rads, just baseboard pipes.