Microsoft.Graph.Communications.Core.Exceptions.ServiceException: Code: 8522

Describe the issue
My bot subscribes to unhandled exceptions and I receive regularly the error: Microsoft.Graph.Communications.Core.Exceptions.ServiceException: Code: 8522

Expected behavior
The call is stopped but I still receive this error

Graph SDK (please complete the following information):
Microsoft.Graph.Communications.Calls.Media 1.2.0.1702

Call ID
ec8cbd23-e6cf-4095-bf0c-d91192e40968

Logs
A task has encountered an unobserved exception
System.AggregateException: A Task's exception(s) were not observed either by Waiting on the Task or accessing its Exception property. As a result, the unobserved exception was rethrown by the finalizer thread. ---> Microsoft.Graph.Communications.Core.Exceptions.ServiceException: Code: 8522
Message: Call not found.
Scenario Id: ec8cbd23-e6cf-4095-bf0c-d91192e40968
Inner error:
AdditionalData:
date: 2020-09-17T11:34:41
request-id: 8f232da6-2d74-4133-ba3d-7cc4b52dbc7b
client-request-id: ede4d02e-018b-4d3e-97a5-30c6fc0e2e95
---> Microsoft.Graph.Communications.Core.Exceptions.ServiceException: Code: 8522
Message: Call not found.
Inner error:
AdditionalData:
date: 2020-09-17T11:34:41
request-id: 8f232da6-2d74-4133-ba3d-7cc4b52dbc7b
client-request-id: ede4d02e-018b-4d3e-97a5-30c6fc0e2e95

at Microsoft.Graph.Communications.Client.Transport.GraphAuthClient.d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.Graph.Communications.Client.Transport.GraphAuthClient.d__42.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Graph.Communications.Common.Transport.GraphHttpClient.<SendAsync>d__241.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.Graph.Communications.Client.Transport.GraphClientWrapper.d__121.MoveNext() --- End of inner exception stack trace --- at Microsoft.Graph.Communications.Client.Transport.GraphClientWrapper.<ValidateAndWrapAsync>d__121.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.Graph.Communications.Client.Transport.GraphClientWrapper.d__10`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.Graph.Communications.Calls.StatefulCall.d__25.MoveNext()
--- End of inner exception stack trace ---
---> (Inner Exception #0) Status Code: NotFound
Microsoft.Graph.Communications.Core.Exceptions.ServiceException: Code: 8522
Message: Call not found.
Scenario Id: ec8cbd23-e6cf-4095-bf0c-d91192e40968
Inner error:
AdditionalData:
date: 2020-09-17T11:34:41
request-id: 8f232da6-2d74-4133-ba3d-7cc4b52dbc7b
client-request-id: ede4d02e-018b-4d3e-97a5-30c6fc0e2e95
---> Microsoft.Graph.Communications.Core.Exceptions.ServiceException: Code: 8522
Message: Call not found.
Inner error:
AdditionalData:
date: 2020-09-17T11:34:41
request-id: 8f232da6-2d74-4133-ba3d-7cc4b52dbc7b
client-request-id: ede4d02e-018b-4d3e-97a5-30c6fc0e2e95

at Microsoft.Graph.Communications.Client.Transport.GraphAuthClient.d__5.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.Graph.Communications.Client.Transport.GraphAuthClient.d__42.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Microsoft.Graph.Communications.Common.Transport.GraphHttpClient.<SendAsync>d__241.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.Graph.Communications.Client.Transport.GraphClientWrapper.d__121.MoveNext() --- End of inner exception stack trace --- at Microsoft.Graph.Communications.Client.Transport.GraphClientWrapper.<ValidateAndWrapAsync>d__121.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.Graph.Communications.Client.Transport.GraphClientWrapper.d__10`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.Graph.Communications.Calls.StatefulCall.d__25.MoveNext()<---

The stack trace names StatefulCall.KeepAliveAsync, GraphClientWrapper, and GraphAuthClient.ValidateResponseAsync; start there and trace how the stopped call's 8522 response reaches an unobserved task. Done would mean the stopped call no longer produces an unobserved "Call not found" exception.