ball

Project/Assets/ML-Agents/Examples/Tennis/Scripts/TennisArea.cs

     {
         var ballOut = Random.Range(12.5f, 14f);
         var flip = Random.Range(0, 2);
+        var serve = 1f;
-            ball.transform.position = new Vector3(-ballOut, 1f, 0f) + transform.position;
-        }
-        else
-        {
-            ball.transform.position = new Vector3(ballOut, 1f, 0f) + transform.position;
+            serve = -1f;
-        m_BallRb.velocity = new Vector3(0f, 20f, 0f);
+        ball.transform.position = new Vector3(serve * ballOut, 1f, 0f) + transform.position;
+        m_BallRb.velocity = new Vector3(serve * 2f, 20f, 0f);
         ball.transform.localScale = new Vector3(.5f, .5f, .5f);
         m_BallScript.ResetPoint();
     }

config/trainer_config.yaml

         window: 10
         play_against_latest_model_ratio: 0.5
         save_steps: 50000
-        swap_steps: 2000
+        swap_steps: 50000
         team_change: 100000
 
 Goalie: