Wedge possibly cracked (and toast) and that's jamming things? Here's a couple photos of the parts: in the first, Stem, with screw and steel wedge installed and also lying on the side, and the "white metal" wedge/clamp that fits against the bar. That one's cracked.



In the second, three bar wedges, two of them cracked -- shows that they don't always fail in the same place.