Let's go flying   

If you experts have any experience flying fast at high altitude  FL 250 and above you have an idea how strong clear air turbulence can be.   If it was an autopilot glitch I would think it would be a Phugoid type manuever not something that would pin people on the ceiling.  Why did people in their seats have their belts off in the first place.  Do you take your seat belt off once you get moving in your car.  If they were all walking around the cabin the trim couldn't keep up and that is an airline problem not the airplane .   For what it is worth all the problems Boeing is having is from Pizzing off someone in the Goverment or DOD.