When an avatar uses a custom animation controller in the base layer for movement, and use the vrc tracking controller component to enforce head tracking and hand tracking. It will missalign the hands from the controller and the head doesn't track at all and instead is using an animation. rather than the headset orientation/position.
in the video i show the behaviour of the new IK and the legacy IK. Specifically look at the head and the hands when moving.
This is what the tracking controller looks like for the avatar in the video
There is an exception where the hands will resync with the controller position after 1 or two seconds. but only if the "Force Locomotion animations for 6 point tracking" option is enabled on the avatar descriptor.
If it is dissabled the hands will always be desynced while moving.