no latest model

Project/Assets/ML-Agents/Examples/Tennis/Materials/Physic_Materials/bounce.physicMaterial

 --- !u!134 &13400000
 PhysicMaterial:
   m_ObjectHideFlags: 0
-  m_PrefabParentObject: {fileID: 0}
-  m_PrefabInternal: {fileID: 0}
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
-  frictionCombine: 0
-  bounceCombine: 0
+  frictionCombine: 1
+  bounceCombine: 3

config/ppo/Tennis.yaml

         gamma: 0.995
     self_play:
       window: 10
-      play_against_latest_model_ratio: 0.5
+      play_against_latest_model_ratio: 0.0
       save_steps: 100000
       swap_steps: 2000
       team_change: 200000