This is what my balance bar looks like, it doesn't seem to have any problems with the string or spring. I just include it to help people identify what I've got.
One more clue is that on a good window I can see the top of the part that is broken on the window that doesn't stay open. Here it is.
I'm searching but can't find a good replacement for that piece. I think a big contributor to my failed search is I don't know what that piece is called. Does anyone know what that piece is called and better yet where to get them?