Google Play Quests - Claiming reward occurs crash in unity 4.6.9

Hi, I have entered same issue to here also but couldn't get any reply.

I am trying to use the quest functionalities of newest google play services plugin (v.0.9.31a) in unity 4.6.9 on Android. Everything is fine with authentication , leaderboard and viewing default quest UI, but when I try to accept a quest or claim a reward game crashes or close the quest window.

I suppose that something wrong occurs when quest callback events triggered. But I couldn't find out what is wrong.

 I/Unity (11512): UserRequestsMilestoneClaiming
 I/Unity (11512):
 
 I/Unity (11512): (Filename: ./artifacts/AndroidManagedGenerated/UnityEngineDebug.cpp Line: 56)
 I/Unity (11512): 
 W/google-breakpad(11512): ### ### ### ### ### ### ### ### ### ### ### ### ###
 W/google-breakpad(11512): Chrome build fingerprint:
 W/google-breakpad(11512): 4.0
 W/google-breakpad(11512): 13
 W/google-breakpad(11512): 6d6f4589-33a4-4709-9279-1a8b5e855d5c
 W/google-breakpad(11512): ### ### ### ### ### ### ### ### ### ### ### ### ###
 W/InputDispatcher( 721): channel '26cdb719 com.bundleID.example/com.unity3d.player.UnityPlayerProxyActivity (server)' ~ Consumer closed input channel or an error occurred. events=0x9
 D/ConnectivityService( 721): ConnectivityService NetworkRequestInfo binderDied(NetworkRequest [ id=247, legacyType=-1, [ Capabilities: INTERNET&NOT_RESTRICTED&TRUSTED&NOT_VPN] ], android.os.BinderProxy@14cf537)
 E/InputDispatcher( 721): channel '26cdb719 com.bundleID.example/com.unity3d.player.UnityPlayerProxyActivity (server)' ~ Channel is unrecoverably broken and will be disposed!
 W/InputDispatcher( 721): channel '3e3c1178 com.bundleID.example/com.unity3d.player.UnityPlayerNativeActivity (server)' ~ Consumer closed input channel or an error occurred. events=0x9
 E/InputDispatcher( 721): channel '3e3c1178 com.bundleID.example/com.unity3d.player.UnityPlayerNativeActivity (server)' ~ Channel is unrecoverably broken and will be disposed!
 D/ConnectivityService( 721): releasing NetworkRequest NetworkRequest [ id=247, legacyType=-1, [ Capabilities: INTERNET&NOT_RESTRICTED&TRUSTED&NOT_VPN] ]
 I/WindowState( 721): WIN DEATH: Window{26cdb719 u0 com.bundleID.example/com.unity3d.player.UnityPlayerProxyActivity}
 W/InputDispatcher( 721): Attempted to unregister already unregistered input channel '26cdb719 com.bundleID.example/com.unity3d.player.UnityPlayerProxyActivity (server)'
 E/ConnectivityService( 721): RemoteException caught trying to send a callback msg for NetworkRequest [ id=247, legacyType=-1, [ Capabilities: INTERNET&NOT_RESTRICTED&TRUSTED&NOT_VPN] ]
 I/WindowState( 721): WIN DEATH: Window{3e3c1178 u0 com.bundleID.example/com.unity3d.player.UnityPlayerNativeActivity}
 W/InputDispatcher( 721): Attempted to unregister already unregistered input channel '3e3c1178 com.bundleID.example/com.unity3d.player.UnityPlayerNativeActivity (server)'
 W/WindowManager( 721): Force-removing child win Window{3af170b6 u0 SurfaceView} from container Window{3e3c1178 u0 com.bundleID.example/com.unity3d.player.UnityPlayerNativeActivity}
 W/WindowManager( 721): Failed looking up window
 W/WindowManager( 721): java.lang.IllegalArgumentException: Requested window android.os.BinderProxy@7b63051 does not exist
 W/WindowManager( 721): at com.android.server.wm.WindowManagerService.windowForClientLocked(WindowManagerService.java:8539)
 W/WindowManager( 721): at com.android.server.wm.WindowManagerService.windowForClientLocked(WindowManagerService.java:8530)
 W/WindowManager( 721): at com.android.server.wm.WindowState$DeathRecipient.binderDied(WindowState.java:1142)
 W/WindowManager( 721): at android.os.BinderProxy.sendDeathNotice(Binder.java:551)
 I/WindowState( 721): WIN DEATH: null
 E/libprocessgroup( 721): failed to kill 1 processes for processgroup 11512
 I/ActivityManager( 721): Process com.bundleID.example (pid 11512) has died

Edit:

I have just seen a new kind of error log in adb logs when accepting a quest. Added below :

 W/AppOps  (  721): Bad call: specified package com.google.android.play.games under uid 10107 but it is really 10066
 W/AppOps  (  721): Bad call: specified package com.google.android.play.games under uid 10107 but it is really 10066
 W/Unity   (22092): *** [Play Games Plugin DLL] 03/03/16 14:23:47 +02:00 ERROR: Error encountered executing QuestManager#QuestUICallback. Smothering to avoid passing exception into Native: System.NullReferenceException: Object reference not set to an instance of an object
 W/Unity   (22092):   at GooglePlayGames.Native.NativeQuestClient+<FromQuestUICallback>c__AnonStorey4B.<>m__4B (GooglePlayGames.Native.PInvoke.QuestUIResponse response) [0x00000] in <filename unknown>:0 
 W/Unity   (22092):   at GooglePlayGames.Native.PInvoke.Callbacks+<ToIntPtr>c__AnonStorey85`1[GooglePlayGames.Native.PInvoke.QuestManager+QuestUIResponse].<>m__A8 (IntPtr result) [0x00000] in <filename unknown>:0 
 W/Unity   (22092):   at GooglePlayGames.Native.PInvoke.Callbacks.PerformInternalCallback (System.String callbackName, Type callbackType, IntPtr response, IntPtr userData) [0x00000] in <filename unknown>:0 
 W/Unity   (22092):  
 W/Unity   (22092): (Filename: ./artifacts/AndroidManagedGenerated/UnityEngineDebug.cpp Line: 56)
 W/Unity   (22092): 
 I/Unity   (22092):  [Play Games Plugin DLL] 03/03/16 14:23:47 +02:00 DEBUG: Entering internal callback for QuestManager#AcceptCallback
 I/Unity   (22092):  
 I/Unity   (22092): (Filename: ./artifacts/AndroidManagedGenerated/UnityEngineDebug.cpp Line: 56)
 I/Unity   (22092): 
 W/art     (22092): 0x9937ab40
 W/art     (22092): 0x9937ab50
 W/art     (22092): 0x9937ab10
 W/art     (22092): Native thread exiting without having called DetachCurrentThread (maybe it's going to use a pthread_key_create destructor?): Thread[43,tid=22622,Native,Thread*=0x8e2d1c00,peer=0x12da40a0,"main_dispatch"]
 V/GamesNativeSDK(22092): Detaching from JVM on thread main_dispatch
 E/WifiStateMachine(  721): WifiStateMachine CMD_START_SCAN source -2 txSuccessRate=0,00 rxSuccessRate=0,00 targetRoamBSSID=f4:f2:6d:e0:c9:72 RSSI=-69
 E/WifiStateMachine(  721): WifiStateMachine starting scan for "BLINE_TT_Extended"WPA_PSK with 2442
 I/ClearcutLoggerApiImpl( 9469): disconnect managed GoogleApiClient

UPDATE : This problem is not occur on my samsung note 2 phone which has android 4.4.2 but "sometimes" it still happens on Google Nexus 5 (android 5.1.1). I am trying to figure out what the hell is triggering the crash but couldn't find out. So please, I need help.. :(