Joe, Sorry to see the loss of a nice plane and all of the work.
I have a similar looking bellcrank and have taken it apart. The leads are wrapped around a brass piece and that inserted into the slot for rotation. The brass pieces has a large hole and that is sized down with what seems like soft aluminum. The aluminum sleeve is several thousandths taller than the brass, so the aluminum may be held in the slot by pinch, and then the brass rotate on it. The one that I received was overly tightened and didnt rotate, so disassembled. The bolt is not a sleeve bolt, so threads are against the aluminum, but maybe the aluminum is clamped and doesnt rotate on the threads. Mine was tightened and then didnt rotate in the brass even when loosened. It did rotate on threads.
The bellcrank is shown with the leadouts/shrink hitting the slot. This happens at about 45 50° in either bellcrank position as shown. If you use more bellcrank throw (greater that 45°) for mechanical advantage or because of arm lengths, then you impinge and force the rotation point to the leadout crimp, but similar if wrapped or crimped. There is a forced articulation or rotation in the joiner area if the leadout hits the bellcrank, or if the pivot gets jammed with/by the aluminum.
This is not my field, so my observations and comments may not be correct.