Does not jitter during crouch. Possible jitter during movement, but nearly undetectable.
Note: Jitter occurs while in walking mode, but not in running mode.
Also, one other thing I noticed in this is a slight posture change between the walk and run modes while standing still.
In the walk mode, the character stands a bit more “straight” with knees locked.
While in run mode, the legs are slightly bent at the knee joints.
Although it’s a minor difference, it’s enough to affect the standing physics collision on a flat surface.