<FIRAnalytics / ERROR> Data loss. Unable to write event metadata with Unity Firebase SDK

we tried to integrate firebase parsing into our unity project, but we got the error "Data loss. Unable to write event metadata", don't know how to fix this problem, and ask for help.

Tried the testapp example from https://github.com/firebase/quickstart-unity/tree/master/analytics/testapp but still got the same error.

Here are our tools for integrating firebase analysis into testapp project:

• Download latest SDK 4.0.3 single-firebase
• Open testapp project using Unity 5.5.4f1 (update testapp project from 5.4.1f1)
• Import SDK from firebase-analytics database from FirebaseAnalytics.unitypackage
• Download GoogleService-Info.plist from firebase console and copy to project
• Install single project testapp project and embed it in xcode project
  • Go to iOS platform
  • Disable interleaved engine in iOS build settings in Unity
  • Make TestApp / MainScene.unity3d the first build scene

• Excute command pod install
  
  in build path

  Analyzing dependencies
  Downloading dependencies
  Using Firebase (4.0.4)
  Using FirebaseAnalytics (4.0.2)
  Using FirebaseCore (4.0.4)
  Using FirebaseInstanceID (2.0.0)
  Using GoogleToolboxForMac (2.1.1)
  Using nanopb (0.3.8)
  Generating Pods project
  Skipping User Project Integration
  Sending stats
  Pod installation complete! There are 2 dependencies from the Podfile and 6 total pods installed.
  
        
  
          
          
          
        
  
      

• Open xcode project with xcode 8.3.3
  • Subscription signing configurations
• Build and run on iPhone with iOS 10.3.2

At the exit, we saw a good start:

2017-08-09 14:28:09.611 testapp[1086] <Notice> [Firebase/Analytics][I-ACS023007] Firebase Analytics v.40002000 started
2017-08-09 14:28:09.612 testapp[1086] <Debug> [Firebase/Analytics][I-ACS023009] Debug logging enabled
2017-08-09 14:28:09.667 testapp[1086] <Debug> [Firebase/Analytics][I-ACS023016] Firebase Analytics is ready to receive events
2017-08-09 14:28:09.884 testapp[1086] <Notice> [Firebase/Analytics][I-ACS003007] Successfully created Firebase Analytics App Delegate Proxy automatically. To disable the proxy, set the flag FirebaseAppDelegateProxyEnabled to NO in the Info.plist

      

        
        
        
      

    

Then some errors came up when firebase started logevent:

2017-08-09 14:28:09.889 testapp[1086] <Warning> [Firebase/Analytics][I-ACS012011] Received empty measurement bundle metadata for getting dictionary representation
2017-08-09 14:28:09.890 testapp[1086] <Error> [Firebase/Analytics][I-ACS023068] Data loss. Cannot record event metadata. Error: Error Domain=com.google.gmp.measurement.ErrorDomain Code=2 "Failed to insert/update unknown data type" UserInfo={NSLocalizedDescription=Failed to insert/update unknown data type}
2017-08-09 14:28:09.890 testapp[1086] <Error> [Firebase/Analytics][I-ACS034010] Transaction failed

      

        
        
        
      

    

And here is the complete log in essence. Appreciate any help, thanks.