AI PathState

Hi folks, I'm trying to detect when my AI guy can't reach his destination. To do so, I'm using this code:

 IEnumerator ReRouteAI(  )
 {
     agent.SetDestination (goal.transform.position);
     agent.Resume ();

     // Wait to generate path
     while (agent.pathPending) {
         Debug.LogWarning ("Waiting for Path");
         yield return null;
     }
     Debug.LogWarning ("Path calculated");
     Debug.LogWarning (" PathState: " + agent.pathStatus);
 }

The issue I'm facing, is even when the path is obviously not complete (ie the AI has moved as close to the destination as he can and stops ) its reporting agent.pathstatus is always pathcomplete (I was expecting pathpartial. He's drawing a debug line to his target, so I know the his destination isn't being affected.

Any ideas as to why this is happening? Many Thanks