[thstone]

That is an easy and relatively cheap place to start but I didn't see that much play in the video.

A big clunk over bumps is usually the main lower control arm bushings. They might seem tight when pulled on by hand but try putting the car on jackstands and then raising the suspension using a floor jack and check the smoothness of the rear LCA operation through its travel. If its rough or grindy, then that is your problem.