The problem here is that the project is using SmartUpdate and messing with the timescale. These two things are not compatible, because when the time is resumed after being paused, SmartUpdate - which attempts to dynamically deduce the nature of the target's motion - gets confused about how the target is moving.
The solution is to decide how you want the camera to update (FixedUpdate or LateUpdate) and set that mode, while making sure that the target moves only on the desired clock.
In this scene, there are 2 choices to make the motion smooth:
Set the CMBrain to update on FixedUpdate.
Alternatively, enable Interpolation on the Cube's Rigidbody, and put the Brain in LateUpdate mode. If you do this, be sure to move the cube only in ways that are compatible with Rigidbody Interpolation. Generally, this alternative will produce smoother results than the FixedUpdate approach, because camera frames and render frames will be synchronized.
Note: always test motion smoothness in a build, to eliminate artifacts caused by the Unity editor's tendency to produce uneven frame rates.