Many thanks for your help, guys! Yes, the nut spinned inside its socket. Almost as soon as I unscrewed. I guess "plastic" socket is a rather fragile thing...That's why this kind of design is very rare everywhere else! Anyway, Jani gave me a new baseplate (thanks again! It's nice of you). But it took...

Thanx Jani!

I've got a brand new pair of Seismic 135mm trucks. Some weeks ago, I changed the springs of one of the trucks and I had no problem, although it's not easy. Then I tried to change the springs of the other truck. Almost as soon as I unscrewed the pivot pin, the nut started to turn inside its hole. Now...