Child rigidbody acting strange when moving parent.

I'm working on a space exploration game and have made the player (a rigidbody) a child of the current planet. In order to keep the level of precision high I make sure that the current planet is always at (0,0). This is the code that handles that:

 public class SystemMotion : MonoBehaviour
 {
     public Transform system;
     public Transform planet1;
     public Transform sun;
     public PlayerController player;
 
     private void FixedUpdate()
     {
         planet1.RotateAround(sun.position, new Vector3(0, 1, 0), 10 * Time.deltaTime);
         planet1.Rotate(new Vector3(0, 1, 0)*Time.deltaTime);
 
         Recenter();
     }
 
     void Recenter()
     {
         system.Rotate(-player.target.rotation.eulerAngles);
         system.position -= player.target.position;
     }
 }
 

And this is the result: https://imgur.com/i6kKjy8

The rigidbodies are moving on their own despite the planet staying perfectly still.

Everything works fine when the SystemMotion script is inactive.