Forgive me if I use the wrong terminology.

I have a cylinder/crane from an 1920s M&P. The pin in the very center does not move - at all. In one working correctly, you can move it and feel spring tension against it.

So, I am curious what to do about it. My first try is going to be to soak it in Kroil for a couple of days. If it is still stuck, does anyone have any suggestions?