OK, ya. It's a tough one. I like the idea of the wood blocks for a test to see if there is change. What's your angles before and after. Turn the shaft to shut me up! It's possible the yoke fixed the problem and caused another one. I've seen more annoying stuff. Do the shaft twice. Once 180. And once only turning the rear yoke 180. See what happens. Will only take less than a half hour maybe fifteen minutes. It's free! That's what I would do next. I am cheap and lazy. I do the easy stuff and free stuff first. Plus these exercises get you to thinking. Then keep on going.
j