I looked at the video. No sound here at work so could not get the full effect.
A couple of things I noticed.
Picture quality is very good.
I did not see a dial indicator present ? No way to measure the proper gear to gear backlash without one. The spec. is in thousandths of an inch. Even with the wood blocks in place I saw the gears move out of position while you measured the fan blade.
While it looked supported good laying down the fanshaft to gov. case angle will effect the backlash. That's why John Deere in their shop manuals (there is a great one on the late B)clamp the gov. case edge in a vise and have the fanshaft pointing straight up into the air this way it will seek center better without any weight against it.