I've seen a strange behavior in AE CS5 occasionally: when rendering a large comp (4096px x 2160px) at full resolution in which a light is turned on and casting shadows from and to large layers (example 6000px x 8000px), the resultant shadows sometimes vibrate as if AE is hunting for the correct position of the light from which to calculate the shadow casting.
The behavior is not easily repeatable and seems to happen with spot lights as well as parallel lights. It seems to occur with lights close in a scene or far away. It seems to go away if what's being rendered is a moving camera's point-of-view. In one particular render with a light far away I saw it appear as the camera came to a smooth stop. In another with a close light and generally static camera (just some 3D handheld motion) the vibration was pronounced until the moment the camera began a fast crane up. Then it stopped completely.
Rendering was done with OpenGL off, Render Multiple Frames Simultaneously off, Windows 7 and 24gb RAM.
I'd like to be able to stop this behavior. Any thoughts or info will be much appreciated.