Stuttering with moving Rigidbody

Hi! My name is Raúl. First of all, sorry for my english.

I am getting a lot of stuttering when moving my character with rigidbody.MovePosition. I have tried changing the "interpolate" property of the rigidbody to Interpolate and extrapolate, but behaves the same.

My Fixed Timestep is 0.02 (default), if I get this value down, the stuttering stops, but I don't want to use this method because I have to turn the value VERY low to work.

I am using Unity 2018.2

You can see the problem in this videos:

https://www.youtube.com/watch?v=g31P70LFYMc

https://www.youtube.com/watch?v=lEMQtbfS1Fk

The videos are recorded at 60fps but my display is 144Hz and it makes it a lot more noticeable. The first example is a simple Unity camera and the second one is the Cinemachine freelook camera, this one is specially bad.

This is my code for the player movement:

 void FixedUpdate()
     {
         rb.MovePosition(rb.position + this.transform.forward * inputMagnitude * speed * Time.fixedDeltaTime);
     }
 
     void Update()
     {
         // Checks if the player is grounded
         isGrounded = Physics.CheckSphere(groundChecker.position, groundDistance, groundLayerMask, QueryTriggerInteraction.Ignore);
 
         // Setup for movement
         if (isGrounded)
         {
             inputs = Vector3.zero;
             inputs.x = GamePad.GetAxis(CAxis.LX);
             inputs.z = GamePad.GetAxis(CAxis.LY);
 
             if (isCrouching)
             {
                 inputs /= 2;
             }
 
             inputMagnitude = inputs.magnitude;
 
             animator.SetFloat("zSpeed", inputMagnitude);
 
             if (mainCamera.isActiveAndEnabled) inputs = mainCamera.transform.TransformDirection(inputs);
 
             inputs.y = 0;
 
             // Rotation changing the forward
             if (inputs != Vector3.zero)
             {
                 this.transform.forward = inputs;
             }
         }
     }