Black screen on Android when using Vuforia inside unity as a library (UaaL)

Hi, I am trying to run Vuforia inside Unity embedded as a library (UaaL) in a native project. I am using the guideline provided here: 

https://library.vuforia.com/content/vuforia-library/en/articles/Solution/using-vuforia-engine-with-unity-as-a-library.html

When i run on android, it works fine for the first time.

When i unload Vuforia and then try to launch it again, i see a black screen. Here is the stack trace i see::

Start Vuforia Engine     (Filename: ./Runtime/Export/Debug/Debug.bindings.h Line: 35) 2020-03-05 06:15:37.242 20557-20597/com.example.native_x_unity:Unity E/libc: Access denied finding property "persist.vendor.camera.privapp.list" 2020-03-05 06:15:37.233 20557-20557/com.example.native_x_unity:Unity W/UnityMain: type=1400 audit(0.0:977): avc: denied { read } for name="u:object_r:persist_camera_prop:s0" dev="tmpfs" ino=23725 scontext=u:r:untrusted_app_27:s0:c151,c257,c512,c768 tcontext=u:object_r:persist_camera_prop:s0 tclass=file permissive=0 2020-03-05 06:15:37.266 20557-20597/com.example.native_x_unity:Unity D/Vuforia: cameraDeviceStartCamera 2020-03-05 06:15:37.401 20557-20597/com.example.native_x_unity:Unity I/AR: Starting camera with profile for default, 0 2020-03-05 06:15:37.408 20557-20597/com.example.native_x_unity:Unity W/Unity: Unsupported screen orientation UNKNOWN, returning default orientation 'LandScapeLeft'     (Filename: ./Runtime/Export/Debug/Debug.bindings.h Line: 35) 2020-03-05 06:15:37.441 20557-20597/com.example.native_x_unity:Unity E/Unity: Exception in callback: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.NullReferenceException: Object reference not set to an instance of an object       at Vuforia.AndroidUnityPlayer.CheckOrientation () [0x0002b] in <f54e84437e1c49e49df3289b7f192132>:0       at Vuforia.AndroidUnityPlayer.Update () [0x00027] in <f54e84437e1c49e49df3289b7f192132>:0       at Vuforia.VuforiaARController.UpdateStatePrivate (System.Boolean forceUpdate, System.Boolean reapplyOldState) [0x00027] in <f54e84437e1c49e49df3289b7f192132>:0       at Vuforia.VuforiaARController.UpdateState (System.Boolean forceUpdate, System.Boolean reapplyOldState) [0x0000c] in <f54e84437e1c49e49df3289b7f192132>:0       at Vuforia.DigitalEyewearARController.Update () [0x00000] in <f54e84437e1c49e49df3289b7f192132>:0         at (wrapper managed-to-native) System.Reflection.MonoMethod.InternalInvoke(System.Reflection.MonoMethod,object,object[],System.Exception&)       at System.Reflection.MonoMethod.Invoke (System. 2020-03-05 06:15:37.459 20557-20597/com.example.native_x_unity:Unity I/chatty: uid=10407(com.example.native_x_unity) UnityMain identical 2 lines 2020-03-05 06:15:37.465 20557-20597/com.example.native_x_unity:Unity E/Unity: Exception in callback: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.NullReferenceException: Object reference not set to an instance of an object       at Vuforia.AndroidUnityPlayer.CheckOrientation () [0x0002b] in <f54e84437e1c49e49df3289b7f192132>:0       at Vuforia.AndroidUnityPlayer.Update () [0x00027] in <f54e84437e1c49e49df3289b7f192132>:0       at Vuforia.VuforiaARController.UpdateStatePrivate (System.Boolean forceUpdate, System.Boolean reapplyOldState) [0x00027] in <f54e84437e1c49e49df3289b7f192132>:0       at Vuforia.VuforiaARController.UpdateState (System.Boolean forceUpdate, System.Boolean reapplyOldState) [0x0000c] in <f54e84437e1c49e49df3289b7f192132>:0       at Vuforia.DigitalEyewearARController.Update () [0x00000] in <f54e84437e1c49e49df3289b7f192132>:0         at (wrapper managed-to-native) System.Reflection.MonoMethod.InternalInvoke(System.Reflection.MonoMethod,object,object[],System.Exception&)       at System.Reflection.MonoMethod.Invoke (System.

Could you let me know if i am missing anything? Any help would be greatly appreciated. Thanks