Dancing shadows

I have what I hope to be an easy problem to fix. My scene has real time lighting, a cinemachine virtual camera, and a light source that is set to real time with soft shadows enabled. If I set the camera to look at my main player, the shadows dance around (as if the light source were changing directions erratically). If I change the look at target to nothing, the shadows behave. If I set the target to a stationary object, there will be some "dancing", but it will eventually settle down.

At first, I thought I was getting some weird z-fighting, but I narrowed it down to the Cinemachine camera. If I step through time, I can watch the shadows change orientation from one frame to the next.

EDIT: Incidentally, the objects in the scene appear to be fine (e.x. no jittering, etc.) I am additively loading the scene, so I don't know if that would affect anything. I've also tried changing the various update stages of the brain. Nothing, short of changing the look at target to null, fixes the problem.

Currently using Unity 2020.1.1f1 with Cinemachine 2.6.3

 

After some more investigation, I've narrowed it down further. The problem can only be seen if the look at value is set. My particular look at object is a physics-based object, but I don't think that's the issue based on my investigation.

Changing the near plane value of the virtual camera can cause the problem to nearly disappear when using a value of 1.0, but using values less than 0.5 are where problems start. The attached image illustrates this. The higher the value for the near plane, the better the behavior of the shadows.

If the look at target is null, then there aren't any problems at all regardless of the near plane value.

 

its been a year and i hope you solved your problem

but that looks like a standard shadow acne problem.
ramp up depth bias and normal bias. mostly setting normal bias higher than 0.1 will do this.

https://docs.unity3d.com/Manual/ShadowPerformance.html