Problem with calculating potential and kinetic energy

Hello everyone. I need to calculate the mechanical energy of orbiting body , which is a sum of kinetic and potential energy. Mechanical energy should be constant, but for some reason, it isn't.

This is my problem. I don't know why, but the mechanical energy changes, when the object is moving closer/farther from the influencer. I tried calculating everything on double precision numbers, but it didn't work.

 public class OrbitingBody : MonoBehaviour { 
 
     Rigidbody influencer;
     Rigidbody rigidbody;
     public float mechanicalEnergy;
     public float gravityConstant;
   
     void Start () {
         influencer = FindObjectOfType<Influencer>().GetComponent<Rigidbody>();
         rigidbody = GetComponent<Rigidbody>();
     }
     
     void FixedUpdate () {
         mechanicalEnergy = Energy(influencer); 
    }
 
     float Energy(Rigidbody other)
     {
         float Ek = rigidbody.mass * rigidbody.velocity.sqrMagnitude / 2; // kinetic energy
         float Ep = -gravityConstant * rigidbody.mass * other.mass / (other.transform.position - transform.position).magnitude; // potential energy
 
         return Ek+Ep; // mechanical energy of an object;
     }}

}

 public class Influencer : MonoBehaviour {
 
     Rigidbody[] rigidbodies;
     Rigidbody rigidbody;
     public float gravityConstant;
 
     void Start () {
         rigidbodies = FindObjectsOfType<Rigidbody>() as Rigidbody[];
         rigidbody = GetComponent<Rigidbody>();
     }
 
     void FixedUpdate()
     {
         foreach (Rigidbody rigid in rigidbodies)
         {
             if (rigidbody != rigid)
             {
                 Vector3 dir = rigid.transform.position - transform.position;
                 rigid.velocity += -dir.normalized * gravityConstant * rigidbody.mass / dir.sqrMagnitude * (Time.fixedDeltaTime);
                 
             }
         }
     }
 }