Trying to move Rigidbody2D towards player. Works fine when player is standing still, but once player starts moving, it flips out.

Hello, I'm rotating an enemy to face the player, then moving the enemy forward from it's current position.

And here is a gif of what's happening http://i.imgur.com/q20vGrn.gif

The enemy is the red cube, and the player is the white cube. The enemy object contains a Box Collider 2D, a RigidBody2D, and my EnemyController2D script (below).

It looks like the enemy object is rotating erratically whenever the player moves, so when it tries to move towards the player it spins around in a circle, but I don't understand why it's doing that.

Here is my code:

 using UnityEngine;
 using System.Collections;
 
 public class EnemyController2D : MonoBehaviour {
 
     public float moveSpeed = 3;
 
     Rigidbody2D rbody;
     public GameObject player;
     Vector2 velocity;
 
     void Start () {
         rbody = GetComponent<Rigidbody2D> ();
     }
 
     void FixedUpdate(){
         Vector3 dir = player.transform.position - transform.position;
         float angle = Mathf.Atan2(dir.y,dir.x) * Mathf.Rad2Deg - 90;
 
         rbody.MoveRotation (angle);
 
         Vector2 moveForward = new Vector2 (Mathf.Cos (angle), Mathf.Sin (angle));
 
         rbody.MovePosition(rbody.position + moveForward * moveSpeed * Time.fixedDeltaTime);
     }
 }

Thanks