After updating to Cinemachine 2.2 via the package manager, I noticed varying degrees of jitter anywhere that a Cinemachine camera transition starts or ends (but no problems during the transition phase itself).
After reverting back to 2.1.13, the problem goes away.
This happens while scrubbing, as well as in Play Mode.
I’m running Unity 2018.2 B10.
Here’s a short video clip to demonstrate: