Is there something obvious I'm missing?
For the rear mechanism, keep in mind it is 55 years old. I would remove the parallelogram spring and make sure the body moves freely without spring tension, I would even back off the adjuster screws to verify this, feed it oil too.
These bodies usually do not have a lot of unwanted torsional play, but test, don't guess.
I would be tempted to do as I did for my earlier unit, and move the jockey cage to the jockey cage next spring tension port, the aim is to increase the spring tension throughout, makes for snappier shifts.
Otherwise, the same guidance applies, adjust the hangar to insure its perpendicularity to the wheel, (even if using a claw, and especially if using one).
In the road to 10,000… then T-Mar land