Players stutters when attached to fixed joint

I have a rock that slides down a hill, this is controlled using an animation (I used to do it using physics and low friction materials, but got some unwanted behaviour 5% of the time).
In order for my player to stay attached to the rock during the slide, I am using a fixed joint in the middle of the rock (The joint is a child of the rock, the rock has no RB).
While the player stays attached, it stutters a lot and also drags a bit behind, looks very un-natural. The rock does move quite fast.
Unfortunately adding the player as a child-object of the rock is not an option.

player RB:


Joint:


Does anyone have any ideas what could be causing it?

 

As the rock has no RB then the fixed joint attaches the player to the world. You may add a kinematic Rigidbody to the rock and attach the joint to it (Connected Body). Then animate the rock and translate the pose to the rb via Rigidbody.MovePosition and Rigidbody.MoveRotation (from FixedUpdate).

 

Thanks, think simply setting Update mode to "Update Physics" instead of Normal seems to have solved it

?