Bullet Physics is not helping me...

You can see the jittering when moving characters on a flat surface:

https://www.youtube.com/watch?v=TytxCKteU70

I'm trying to fix the jittering when moving a character. I was using the bullet's btKinematicCharacterController, but since it was nearly impossible to get it right, I moved to a RigidBody implementation (that you can see in this video). But I'm not getting any better with it. :/